INTERNET-DRAFT Adam M. Costello draft-ietf-idn-amc-ace-w-00.txt 2001-May-31 Expires 2001-Nov-30 AMC-ACE-W version 0.1.0 Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html Distribution of this document is unlimited. Please send comments to the author at amc@cs.berkeley.edu, or to the idn working group at idn@ops.ietf.org. A non-paginated (and possibly newer) version of this specification may be available at http://www.cs.berkeley.edu/~amc/charset/amc-ace-w Abstract AMC-ACE-W is a reversible transformation from a sequence of Unicode [UNICODE] code points to a sequence of letters, digits, and hyphens (LDH characters). AMC-ACE-W could be used as an ASCII-Compatible Encoding (ACE) for internationalized domain names [IDN] [IDNA]. Besides domain names, there might also be other contexts where it is useful to transform Unicode characters into "safe" (delimiter-free) ASCII characters. (If other contexts consider hyphens to be unsafe, a different character could be used to play its role, like underscore.) Contents Features Name Terminology Description Base-32 characters Encoding and decoding algorithms Signature Mixed-case annotation Comparison with other ACEs Example strings Security considerations Acknowledgements References Author Example implementation Features Completeness: Every Unicode string maps to an LDH string. Restrictions on which Unicode strings are allowed, and on length, may be imposed by higher layers. Uniqueness: Every Unicode string maps to at most one LDH string. Reversibility: Any Unicode string mapped to an LDH string can be recovered from that LDH string. Efficient encoding: The ratio of encoded size to original size is small for all Unicode strings. This is important in the context of domain names because [RFC1034] restricts the length of a domain label to 63 characters. Simplicity: The encoding and decoding algorithms are reasonably simple to implement. The goals of efficiency and simplicity are at odds; AMC-ACE-W aims at a reasonable balance between them. Mixed-case annotation: Even if the Unicode string has been case-folded prior to encoding, it is possible to used mixed case in the encoded string as an annotation telling how to convert the folded Unicode string into a mixed-case Unicode string for display purposes. This feature is optional; see section "Mixed-case annotation". Readability: The letters A-Z and a-z and the digits 0-9 appearing in the Unicode string are represented as themselves in the label. This comes for free because it usually the most efficient encoding anyway. Name AMC-ACE-W is a working name that should be changed if it is adopted. (The W merely indicates that it is the twenty-third ACE devised by this author. BRACE was the third. Most were not worth releasing.) Rather than waste good names on experimental proposals, let's wait until one proposal is chosen, then assign it a good name. Suggestions: UniHost NUDE (Normal Unicode Domain Encoding) UTF-D ("D" for "domain names") UTF-37 (there are 37 characters in the output repertoire) Terminology LDH characters are the letters A-Z and a-z, the digits 0-9, and hyphen-minus. A quartet is a sequence of four bits (also known as a nibble or nybble). A quintet is a sequence of five bits. Hexadecimal values are shown preceeded by "0x". For example, 0x60 is decimal 96. As in the Unicode Standard [UNICODE], Unicode code points are denoted by "U+" followed by four to six hexadecimal digits, while a range of code points is denoted by two hexadecimal numbers separated by "..", with no prefixes. "x..y" means the range of integers x through y inclusive. "x << y" means x left-shifted by y bits (equivalent to x times 2 to the power y), and "x >> y" means x right-shifted by y bits (equivalent to x divided by 2 to the power y, discarding the remainder). These operations are used only with nonnegative integral values. "x ? y : z" means "y if x is true, z if x is false". It is just like "if x then y else z" except that y and z are expressions rather than statements. Description AMC-ACE-W represents a sequence of Unicode code points as a sequence of LDH characters, although implementations will also need to represent the LDH characters somehow, typically as ASCII octets. The encoder input and decoder output are arrays of Unicode code points (integral values in the range 0..10FFFF, but not D800..DFFF, which are reserved for use by UTF-16). This section describes the representation. Section "Encoding and decoding algorithms" presents the algorithms as commented pseudocode. There is also commented C code in section "Example implementation". The encoded string alternates between two modes: literal mode and base-32 mode. Unicode code points representing LDH characters are encoded as those LDH characters, except that hyphen-minus is doubled. Other Unicode code points are encoded as one or more LDH characters using base-32, in which each character of the encoded string represents a quintet according to the table in section "Base-32 characters". A mode change is indicated by an unpaired hyphen-minus. A pair of consecutive hyphen-minuses represents a hyphen-minus and does not change the mode. In base-32 mode a variable-length code sequence of one to five quintets represents a delta, which is added to a reference point to yield a Unicode code point. There are five reference points, one for each code length. There is also an active style, either 0 or 1. In style 0 the delta is represented by the lowest four bits of each quintet. The highest bit of each quintet is 1, except for the last quintet, where it is 0, allowing the decoder to detect the end of the sequence. Style 0 code sequences: delta from reference point 1: 0xxxx delta from reference point 2: 1xxxx 0xxxx delta from reference point 3: 1xxxx 1xxxx 0xxxx delta from reference point 4: 1xxxx 1xxxx 1xxxx 0xxxx delta from reference point 5: 1xxxx 1xxxx 1xxxx 1xxxx 0xxxx Style 1 is the same as style 0 except that the single-quintet sequence (0xxxx) is not used, and instead a three-quintet sequence (0xxxx xxxxx xxxxx) represents a delta from the third reference point plus 0x1000, effectively increasing the range of deltas that can be used with the third reference point. Style 1 code sequences: delta from reference point 2: 1xxxx 0xxxx delta from reference point 3: 1xxxx 1xxxx 0xxxx delta from ref.pt.3 + 0x1000: 0xxxx xxxxx xxxxx delta from reference point 4: 1xxxx 1xxxx 1xxxx 0xxxx delta from reference point 5: 1xxxx 1xxxx 1xxxx 1xxxx 0xxxx For each reference point, the delta can range from 0 to some maximum value determined by the available bits in the code sequence, so each reference point is the bottom of a window of code points. The maximum delta for each window depends on the style: Style 0 maximum deltas: window 1: 0xF window 2: 0xFF window 3: 0xFFF window 4: 0xFFFF window 5: 0xFFFFF Style 1 maximum deltas: window 2: 0xFF window 3: 0x4FFF window 4: 0xFFFF window 5: 0xFFFFF A code point is encoded as an offset into one of the windows of the active style, the smallest window that contains it. Reference points 4 and 5 are fixed at 0 and 0x10000 respectively, so that windows 4 and 5 always cover the entire Unicode code space 0..10FFFF. The other reference points and the active style are updated whenever a code point has been encoded or decoded in base-32 mode, using following heuristic. Let n denote the code point, and let k denote the number of base-32 characters that were used to represent it. The active style is: set to 0 if k is less than 3, unchanged if k equals 3, set to 1 if k is more than 3. Reference point 1 is: set to n rounded down to a multiple of 0x10. Reference point 2 is: unchanged if k is 2 or less, else set to 0xA0 if n is in A0..17F, else set to n rounded down to a multiple of 0x100. Reference point 3 is: unchanged if k is 3 or less, else set to 0x4E00 if n is in 3000..9FFF, else set to 0x8800 if n is in A000..D7FF and the new active style is 1, else set to n rounded down to a multiple of 0x1000. The initial values of the state variables are: mode: base-32 active style: 0 reference point 1: 0xE0 reference point 2: 0xA0 reference point 3: 0 reference point 4: 0 reference point 5: 0x10000 Base-32 characters "a" = 0 = 0x00 = 00000 "s" = 16 = 0x10 = 10000 "b" = 1 = 0x01 = 00001 "t" = 17 = 0x11 = 10001 "c" = 2 = 0x02 = 00010 "u" = 18 = 0x12 = 10010 "d" = 3 = 0x03 = 00011 "v" = 19 = 0x13 = 10011 "e" = 4 = 0x04 = 00100 "w" = 20 = 0x14 = 10100 "f" = 5 = 0x05 = 00101 "x" = 21 = 0x15 = 10101 "g" = 6 = 0x06 = 00110 "y" = 22 = 0x16 = 10110 "h" = 7 = 0x07 = 00111 "z" = 23 = 0x17 = 10111 "i" = 8 = 0x08 = 01000 "2" = 24 = 0x18 = 11000 "j" = 9 = 0x09 = 01001 "3" = 25 = 0x19 = 11001 "k" = 10 = 0x0A = 01010 "4" = 26 = 0x1A = 11010 "m" = 11 = 0x0B = 01011 "5" = 27 = 0x1B = 11011 "n" = 12 = 0x0C = 01100 "6" = 28 = 0x1C = 11100 "p" = 13 = 0x0D = 01101 "7" = 29 = 0x1D = 11101 "q" = 14 = 0x0E = 01110 "8" = 30 = 0x1E = 11110 "r" = 15 = 0x0F = 01111 "9" = 31 = 0x1F = 11111 The digits "0" and "1" and the letters "o" and "l" are not used, to avoid transcription errors. All decoders must recognize both the uppercase and lowercase forms of the base-32 characters (including mixtures of both forms). An encoder should output only lowercase forms or only uppercase forms unless it uses the feature described in section "Mixed-case annotation"). Encoding and decoding algorithms All ordering of bits, quartets, and quintets is big-endian (most significant first). When subroutines alter variables that are passed in as arguments, those changes are seen by the caller after the subroutine returns. procedure initialize(refpoint,style,literal): let refpoint[1..5] = (0xE0, 0xA0, 0, 0, 0x10000) let style = 0 let literal = false procedure update(refpoint,style,n,k): # Update the active style and reference points based on # the latest code point (n) and the number of base-32 # characters used to represent it (k). let style = k < 3 ? 0 : k > 3 ? 1 : style let refpoint[1] = (n >> 4) << 4 if (k > 2) then let refpoint[2] = n is in 00A0..017F ? 0xA0 : (n >> 8) << 8 if (k > 3) then let refpoint[3] = n is in 3000..9FFF ? 0x4E00 : style == 1 and n is in 0xA000..0xD7FF ? 0x8800 : (n >> 12) << 12 procedure encode: constant maxdelta[0][1..5] = (0xF, 0xFF, 0xFFF, 0xFFFF, 0xFFFFF) constant maxdelta[1][2..5] = ( 0xFF, 0x4FFF, 0xFFFF, 0xFFFFF) initialize(refpoint,style,literal) for each input code point n (in order) do begin # Check code point range to avoid array bounds errors later: if n is not in 0..10FFFF then fail if n == 0x2D then output two hyphen-minuses else if n represents an LDH character then begin # Letter/digit is encoded literally, so get into literal mode. if not literal then output hyphen-minus let literal = true output the character represented by n end else begin # Non-LDH code point is encoded in base-32. # Compute the number of base-32 characters to use: for k = 1 + style to infinity do begin let delta = n - refpoint[k] if delta is in 0..maxdelta[style][k] then break end # Switch to base-32 mode if necessary: if literal then output hyphen-minus let literal = false # Check for the extended delta of style 1 window 3: if k == 3 and delta >= 0x1000 then represent (delta - 0x1000) in base 32 as three quintets else begin # Normal case, four bits per quintet: represent delta in base 16 as k quartets prepend 0 to the last quartet and 1 to each of the others end output a base-32 character corresponding to each quintet update(refpoint,style,n,k) end end procedure decode: initialize(refpoint,style,literal) while the input string is not exhausted do begin read the next character into c # Unpaired hyphen-minus toggles the mode: if c is hyphen-minus and the next character is not then read the next character into c and toggle literal # Double hyphen-minus represents 0x2D: if c is hyphen-minus then read the next character and append 0x2D to history else if literal then append the code point of c to history else begin # Decode a base-32 sequence. convert c to a quintet while a quintet beginning with 0 has not been seen do read and convert up to four more characters concatenate the lowest four bits of each quintet to form delta # Check for the extended delta of style 1 window 3: if style == 1 and there was only one quintet then begin read two characters and convert them to two more quintets concatenate delta and the two quintets to form a new delta let delta = delta + 0x1000 end let k = the number of quintets decoded let n = refpoint[k] + delta output n update(n,k) end end # Enforce the uniqueness of the encoding: encode the output sequence and compare it to the input string fail if they are not equal The decoder must always be prepared for premature end-of-input or invalid input characters, and must either fail immediately or forge ahead and let the comparison at the end fail. The comparison must be case-insensitive if ACEs are always compared case-insensitively (which is true of domain names), case-sensitive otherwise. This check is necessary to guarantee the uniqueness property (there cannot be two distinct encoded strings representing the same sequence of integers). (If the decoder is one step of a larger decoding process, it may be possible to defer the re-encoding and comparison to the end of that larger decoding process.) Signature The issue of how to distinguish ACE strings from unencoded strings is largely orthogonal to the encoding scheme itself, and is therefore not specified here. In the context of domain name labels, a standard prefix and/or suffix (chosen to be unlikely to occur naturally) would presumably be attached to ACE labels. In order to use AMC-ACE-W in domain names, the choice of signature must be mindful of the requirement in [RFC952] that labels never begin or end with hyphen-minus. Since the raw encoded string sometimes begins with a hyphen-minus, the signature must include a prefix that does not begin with hyphen-minus. If the Unicode strings are forbidden from ending with hyphen-minus (which seems prudent anyway), then the raw encoded string will never end with hyphen-minus; otherwise, the signature must include a suffix as well as a prefix. Mixed-case annotation In order to use AMC-ACE-W to represent case-insensitive Unicode strings, higher layers need to case-fold the Unicode strings prior to AMC-ACE-W encoding. The encoded string can, however, use mixed-case base-32 (rather than all-lowercase or all-uppercase as recommended in section "Base-32 characters") as an annotation telling how to convert the folded Unicode string into a mixed-case Unicode string for display purposes. Each non-LDH code point is represented by a sequence of quintets, one of which always begins with 0. When window 3 is used and delta exceeds 0xFFF, the first quintet always begins with 0; in all other cases, the last quintet always begins with 0. The base-32 character representing this quintet is always a letter (as opposed to a digit). If the letter is uppercase, it is a suggestion that the Unicode character be mapped to uppercase (if possible); if the letter is lowercase, it is a suggestion that the Unicode character be mapped to lowercase (if possible). AMC-ACE-W encoders and decoders are not required to support these annotations, and higher layers need not use them. Comparison with other ACEs In this section we compare AMC-ACE-W and eight other ACEs: RACE [RACE03], BRACE [BRACE], LACE [LACE01], AltDUDE [AltDUDE], AMC-ACE-M [AMCACEM], AMC-ACE-O [AMCACEO], AMC-ACE-R [AMCACER], and AMC-ACE-V [AMCACEV]. Some other ACEs are excluded: SACE [SACE] appears obviously too complex, UTF-5 [UTF5] appears obviously too inefficient, UTF-6 [UTF6] can never be more efficient than its similarly simple successor DUDE, and DUDE [DUDE01] is superceded by AltDUDE, which is almost identical but very slightly simpler and very slightly more efficient (and is being considered as the next version of DUDE). Complexity is hard to measure. This author would subjectively rank the complexity of the algorithms (in decreasing order) as: BRACE AMC-ACE-M AMC-ACE-O AMC-ACE-V AMC-ACE-W AMC-ACE-R, RACE LACE AltDUDE All the ACEs support multiple code lengths. In addition, BRACE and AMC-ACE-M use a full arsenal of techniques: pre-scanning the input to select optimal parameters (which must then be encoded at the beginning of the encoded string), literal mode for LDH characters, and a binary mode subdivided into multiple styles. AMC-ACE-O simplifies this by having just one binary style, and reusing procedures for encoding both the parameters and the code points. AMC-ACE-V has two binary styles, and instead simplies by adapting the parameters during encoding/decoding rather than optimizing and declaring them at the start. AMC-ACE-W simplies the adaptation heuristic, while AMC-ACE-R keeps a more sophisticated heuristic but uses a single binary style. RACE and LACE have more than one binary style but no literal mode, and very simple parameter selection/encoding/adaptation mechanisms. AltDUDE has only one binary style, no literal mode (just a trivial exception for hyphen-minus), and very simple parameter adaptation. Implementations can be long and straightforward, or short and subtle, but for whatever it's worth, here are the code sizes of four of the algorithms that were implemented by this author in similar styles: AltDUDE: 114 lines @@@@@@@@@@@@@@@@@@@@@@@ AMC-ACE-R: 150 lines @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ AMC-ACE-W: 156 lines @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ AMC-ACE-V: 176 lines @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ AMC-ACE-O: 214 lines @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ (Not counted in the code sizes are blank lines, lines containing only comments or only a single brace, and wrapper code for testing. BRACE was implemented by this author, but it was a less general implementation, with bounded input and output sizes. AMC-ACE-M was implemented by this author, but in a less compact style.) If a different implementation style were to alter the code sizes additively, or multiplicatively, or a combination thereof, the size differences would retain the same proportions. Mixed-case support: AltDUDE, AMC-ACE-M,O,R,V,W: all characters BRACE: only the letters A-Z, a-z RACE, LACE: none RACE, BRACE, and LACE transform the Unicode string to an intermediate bit string, then into a base-32 string, so there is no particular alignment between the base-32 characters and the Unicode characters. AltDUDE and AMC-ACE-M,O,R,V,W do not have this intermediate stage, and enforce alignment between the base-32 characters and the Unicode characters, which facilitates the mixed-case annotation. The relative efficiency of the various algorithms is suggested by the sizes of the encodings in section "Example strings". The lengths of examples A-K (which are the same sentence translated into a languages from a variety of language families using a variety of scripts) are shown graphically below for each ACE, scaled by a factor of 0.4 so they fit on one line, and sorted so they look like a cummulative distribution. The fictional "Super-ACE" encodes its input using whichever of the other seven ACEs is shortest for that input. RACE: A Arabic 29 @@@@@@@@@@@@ B Chinese 31 @@@@@@@@@@@@ J Taiwanese 31 @@@@@@@@@@@@ D Hebrew 37 @@@@@@@@@@@@@@@ H Russian 47 @@@@@@@@@@@@@@@@@@@ E Hindi 50 @@@@@@@@@@@@@@@@@@@@ F Japanese 60 @@@@@@@@@@@@@@@@@@@@@@@@ I Spanish 66 @@@@@@@@@@@@@@@@@@@@@@@@@@ C Czech 68 @@@@@@@@@@@@@@@@@@@@@@@@@@@ G Korean 79 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ K Vietnamese 112 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ LACE: B Chinese 28 @@@@@@@@@@@ A Arabic 31 @@@@@@@@@@@@ J Taiwanese 31 @@@@@@@@@@@@ D Hebrew 39 @@@@@@@@@@@@@@@@ H Russian 48 @@@@@@@@@@@@@@@@@@@ E Hindi 52 @@@@@@@@@@@@@@@@@@@@@ F Japanese 52 @@@@@@@@@@@@@@@@@@@@@ C Czech 58 @@@@@@@@@@@@@@@@@@@@@@@ I Spanish 68 @@@@@@@@@@@@@@@@@@@@@@@@@@@ G Korean 79 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ K Vietnamese 109 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ AltDUDE: A Arabic 25 @@@@@@@@@@ B Chinese 26 @@@@@@@@@@ D Hebrew 33 @@@@@@@@@@@@@ J Taiwanese 36 @@@@@@@@@@@@@@ H Russian 38 @@@@@@@@@@@@@@@ C Czech 43 @@@@@@@@@@@@@@@@@ F Japanese 49 @@@@@@@@@@@@@@@@@@@@ E Hindi 58 @@@@@@@@@@@@@@@@@@@@@@@ I Spanish 59 @@@@@@@@@@@@@@@@@@@@@@@@ K Vietnamese 81 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ G Korean 89 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ AMC-ACE-R: B Chinese 24 @@@@@@@@@@ A Arabic 28 @@@@@@@@@@@ J Taiwanese 30 @@@@@@@@@@@@ D Hebrew 32 @@@@@@@@@@@@@ C Czech 33 @@@@@@@@@@@@@ H Russian 40 @@@@@@@@@@@@@@@@ F Japanese 42 @@@@@@@@@@@@@@@@@ I Spanish 46 @@@@@@@@@@@@@@@@@@ E Hindi 55 @@@@@@@@@@@@@@@@@@@@@@ K Vietnamese 70 @@@@@@@@@@@@@@@@@@@@@@@@@@@@ G Korean 89 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ AMC-ACE-O: B Chinese 24 @@@@@@@@@@ A Arabic 28 @@@@@@@@@@@ J Taiwanese 30 @@@@@@@@@@@@ D Hebrew 31 @@@@@@@@@@@@ C Czech 34 @@@@@@@@@@@@@@ H Russian 40 @@@@@@@@@@@@@@@@ F Japanese 41 @@@@@@@@@@@@@@@@ I Spanish 49 @@@@@@@@@@@@@@@@@@@@ E Hindi 54 @@@@@@@@@@@@@@@@@@@@@@ K Vietnamese 69 @@@@@@@@@@@@@@@@@@@@@@@@@@@@ G Korean 80 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ AMC-ACE-W: B Chinese 24 @@@@@@@@@@ A Arabic 25 @@@@@@@@@@ J Taiwanese 29 @@@@@@@@@@@@ C Czech 33 @@@@@@@@@@@@@ D Hebrew 33 @@@@@@@@@@@@@ H Russian 38 @@@@@@@@@@@@@@@ I Spanish 46 @@@@@@@@@@@@@@@@@@ F Japanese 47 @@@@@@@@@@@@@@@@@@@ E Hindi 58 @@@@@@@@@@@@@@@@@@@@@@@ K Vietnamese 70 @@@@@@@@@@@@@@@@@@@@@@@@@@@@ G Korean 73 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@ BRACE: B Chinese 22 @@@@@@@@@ A Arabic 26 @@@@@@@@@@ J Taiwanese 27 @@@@@@@@@@@ D Hebrew 33 @@@@@@@@@@@@@ C Czech 36 @@@@@@@@@@@@@@ F Japanese 40 @@@@@@@@@@@@@@@@ H Russian 42 @@@@@@@@@@@@@@@@@ E Hindi 45 @@@@@@@@@@@@@@@@@@ I Spanish 48 @@@@@@@@@@@@@@@@@@@ K Vietnamese 72 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@ G Korean 78 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ AMC-ACE-V: B Chinese 22 @@@@@@@@@ A Arabic 27 @@@@@@@@@@@ J Taiwanese 28 @@@@@@@@@@@ D Hebrew 31 @@@@@@@@@@@@ C Czech 33 @@@@@@@@@@@@@ H Russian 39 @@@@@@@@@@@@@@@@ F Japanese 42 @@@@@@@@@@@@@@@@@ I Spanish 45 @@@@@@@@@@@@@@@@@@ E Hindi 57 @@@@@@@@@@@@@@@@@@@@@@@ K Vietnamese 66 @@@@@@@@@@@@@@@@@@@@@@@@@@ G Korean 72 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@ AMC-ACE-M: B Chinese 23 @@@@@@@@@ J Taiwanese 26 @@@@@@@@@@ A Arabic 28 @@@@@@@@@@@ D Hebrew 31 @@@@@@@@@@@@ C Czech 34 @@@@@@@@@@@@@@ H Russian 38 @@@@@@@@@@@@@@@ F Japanese 42 @@@@@@@@@@@@@@@@@ I Spanish 48 @@@@@@@@@@@@@@@@@@@ E Hindi 54 @@@@@@@@@@@@@@@@@@@@@@ K Vietnamese 69 @@@@@@@@@@@@@@@@@@@@@@@@@@@@ G Korean 71 @@@@@@@@@@@@@@@@@@@@@@@@@@@@ Super-ACE: B Chinese 22 @@@@@@@@@ A Arabic 25 @@@@@@@@@@ J Taiwanese 26 @@@@@@@@@@ D Hebrew 30 @@@@@@@@@@@@ C Czech 33 @@@@@@@@@@@@@ H Russian 38 @@@@@@@@@@@@@@@ F Japanese 40 @@@@@@@@@@@@@@@@ E Hindi 45 @@@@@@@@@@@@@@@@@@ I Spanish 46 @@@@@@@@@@@@@@@@@@ K Vietnamese 69 @@@@@@@@@@@@@@@@@@@@@@@@@@@@ G Korean 71 @@@@@@@@@@@@@@@@@@@@@@@@@@@@ totals: RACE: 610 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ LACE: 595 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ AltDUDE: 537 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ AMC-ACE-R: 489 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ AMC-ACE-O: 480 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ AMC-ACE-W: 476 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ BRACE: 469 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ AMC-ACE-M: 464 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ AMC-ACE-V: 462 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ Super-ACE: 443 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ worst cases: RACE: 112 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ LACE: 109 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ AltDUDE: 89 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ AMC-ACE-R: 89 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ AMC-ACE-O: 80 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ BRACE: 78 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ AMC-ACE-W: 73 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@ AMC-ACE-V: 72 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@ AMC-ACE-M: 71 @@@@@@@@@@@@@@@@@@@@@@@@@@@@ Super-ACE: 71 @@@@@@@@@@@@@@@@@@@@@@@@@@@@ The totals and worst cases above give more weight to languages that produce longer encodings, which arguably yields a good metric (because being efficient for easy languages is arguably less important than being efficient for difficult languages). We can alternatively give each language equal weight by dividing each output length by the corresponding Super-ACE output length. This method yields: totals: RACE: 15.1 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ LACE: 14.7 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ AltDUDE: 13.2 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ AMC-ACE-R: 12.1 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ AMC-ACE-O: 11.9 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ AMC-ACE-W: 11.8 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ BRACE: 11.6 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ AMC-ACE-M: 11.6 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ AMC-ACE-V: 11.5 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ Super-ACE: 11.0 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ worst cases: RACE: 2.06 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ LACE: 1.76 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ AltDUDE: 1.38 @@@@@@@@@@@@@@@@@@@@@@@@@@@@ AMC-ACE-W: 1.29 @@@@@@@@@@@@@@@@@@@@@@@@@@ AMC-ACE-V: 1.27 @@@@@@@@@@@@@@@@@@@@@@@@@ AMC-ACE-R: 1.25 @@@@@@@@@@@@@@@@@@@@@@@@@ AMC-ACE-O: 1.20 @@@@@@@@@@@@@@@@@@@@@@@@ AMC-ACE-M: 1.20 @@@@@@@@@@@@@@@@@@@@@@@@ BRACE: 1.11 @@@@@@@@@@@@@@@@@@@@@@ Super-ACE: 1.00 @@@@@@@@@@@@@@@@@@@@ The results suggest the following conclusions: AltDUDE is preferable to RACE and LACE, because it is a little simpler, is more efficient, and has better support for mixed case. AMC-ACE-M is preferable to BRACE, because it has similar efficiency, is somewhat simpler, and has better support for mixed case. AMC-ACE-V and AMC-ACE-W are both preferable to AMC-ACE-O, because they are more efficient and simpler. AMC-ACE-V is preferable to AMC-ACE-M and BRACE, because it about equally efficient but is quite a bit simpler. AMC-ACE-W is preferable to AMC-ACE-O because it is a little more efficient and quite a bit simpler. AMC-ACE-W may be preferrable to AMC-ACE-R because, although it is slightly more complex, it is significantly better for worst-case CJK inputs, and should be about the same for other inputs. AltDUDE, AMC-ACE-R, AMC-ACE-W, and AMC-ACE-V are progressively more complex and more efficient, and have equal support for mixed case. The choice depends on how much efficiency is required and how much complexity is acceptable. There are three main classes of scripts: single-row (like Arabic and Cyrillic), wide (including Han, which exhibits some locality, and Hangul, which does not), and Latin. (And then there's Japanese, which is a mixture of Han and single-row.) I conjecture that Latin and Hangul names are the most likely to produce long encodings. AltDUDE does well on single-row scripts, and not too bad on the others. The biggest gain when moving from AltDUDE to AMC-ACE-R is in Latin scripts, but other scripts improve a little also. The biggest gain when moving from AMC-ACE-R to AMC-ACE-W is in Hangul, but the worst-case performance improves for CJK in general. AMC-ACE-V provides further improvement across the board, and is more able to adapt to atypical input. Example strings In the ACE encodings below, signatures (like "bq--" for RACE) are not shown. The Unicode code points shown are the ones input to BRACE and AMC-ACE-M,O,R,V,W. The input to RACE, LACE, and AltDUDE is slightly different: LDH characters are first forced to lowercase (which is not necessary for ACEs that encode them literally). UTF-8 and UTF-16 are included for length comparisons, with non-ASCII bytes shown as "?". AMC-ACE-* and AltDUDE are abbreviated AMC-* and ADUDE. Backslashes show where line breaks have been inserted in strings too long for one line. The RACE and LACE encodings are courtesy of Mark Davis's online UTF converter [UTFCONV] (slightly modified to remove the length restrictions). The first several examples are all translations of the sentence "Why can't they just speak in <language>?" (courtesy of Michael Kaplan's "provincial" page [PROVINCIAL]). Word breaks and punctuation have been removed, as is often done in domain names. (A) Arabic (Egyptian): u+0644 u+064A u+0647 u+0645 u+0627 u+0628 u+062A u+0643 u+0644 u+0645 u+0648 u+0634 u+0639 u+0631 u+0628 u+064A u+061F ADUDE: yueqpcycrcyjhbpznpitjycxf AMC-W: ywekhfuhikwdefivejbuiwktr BRACE: 28akcjwcmp3ciwb4t3ngd4nbaz AMC-V: ywekhfuhuiukdefivevjvbuiktr AMC-R: ywekhfuhuikwdwefivevjbuiwktr AMC-O: ageekhfuhuiukdefivevjvbuiktr AMC-M: agiekhfuhuiukdefivevjvbuiktr RACE: azceur2fe4ucuq2eivediojrfbfb6 LACE: cedeisshiutsqksdircuqnbzgeueuhy UTF-16: ?????????????????????????????????? UTF-8: ?????????????????????????????????? (B) Chinese (simplified): u+4ED6 u+4EEC u+4E3A u+4EC0 u+4E48 u+4E0D u+8BF4 u+4E2D u+6587 UTF-16: ?????????????????? AMC-V: w87g8nvk6awispmrwupb6h BRACE: kgcqqsgp26i5h4zn7req5i AMC-M: uqj7g8nvk6awispn9wupdnh AMC-R: w87g8nvk6awisp259eupyx2h AMC-W: w87g8nvk6awisp259esupb6h AMC-O: eqpg8nvk6awisp259eupyx2h ADUDE: w85gvk7g9k2iwf6x9j6x7ju54k UTF-8: ??????????????????????????? LACE: azhnn3b2ybea2aml6qau4libmwdq RACE: 3bhnmtxmjy5e5qcojbha3c7ujywwlby (C) Czech: Pro<ccaron>prost<ecaron>nemluv<iacute><ccaron>esky U+0050 u+0072 u+006F u+010D u+0070 u+0072 u+006F u+0073 u+0074 u+011B u+006E u+0065 u+006D u+006C u+0075 u+0076 u+00ED u+010D u+0065 u+0073 u+006B u+0079 UTF-8: Pro??prost??nemluv????esky AMC-W: -Pro-yp-prost-zm-nemluv-wpyp-esky AMC-V: -Pro-yp-prost-zm-nemluv-wpyp-esky AMC-R: -Pro-yp-prost-tm-nemluv-s8pp-esky AMC-O: piq-Pro-p-prost-9m-nemluv-6pp-esky AMC-M: g26-Pro-p-prost-9m-nemluv-6pp-esky BRACE: i32-Pro-u-prost-8y-nemluv-29f3n-esky ADUDE: tActptyctzpctptnhtyrtzfmibtjd3mt8atyitgtitc UTF-16: ???????????????????????????????????????????? LACE: amaha4tpaeaq2biaobzg643uaearwbyanzsw23dvo3wqcainaqagk43\ lpe RACE: ah7xb73s75xq373q75zp6377op7xig77n37wl73n75wp65p7o3762dp\ 7mx7xh73l754q (D) Hebrew: u+05DC u+05DE u+05D4 u+05D4 u+05DD u+05E4 u+05E9 u+05D5 u+05D8 u+05DC u+05D0 u+05DE u+05D3 u+05D1 u+05E8 u+05D9 u+05DD u+05E2 u+05D1 u+05E8 u+05D9 u+05EA AMC-V: x7ng7eep8e8jfinaqdb8ijp8cb8ij8k AMC-O: afpnqeep8e8jfinaqdb8ijp8cb8ij8k AMC-M: af4nqeep8e8jfinaqdb8ijp8cb8ij8k AMC-R: x7nqeep8e8j7f7inaqdb8ijp8cb8ij8k ADUDE: x5nckajvjpvnpenqpcvjvbevrvdvjvbvd AMC-W: x7nqeep8ej7finaqdb8i7jp8c7b8i7j8k BRACE: 27vkyp7bgwmbpfjgc4ynx5nd8xsp5nd9c RACE: axon5vgu3xsotvoy3tin5u6r5dm53ywr5dm6u LACE: cyc5zxwu2to6j2ov3donbxwt2huntxpc2hunt2q UTF-8: ???????????????????????????????????????????? UTF-16: ???????????????????????????????????????????? (E) Hindi (Devanagari): u+092F u+0939 u+0932 u+094B u+0917 u+0939 u+093F u+0928 u+094D u+0926 u+0940 u+0915 u+094D u+092F u+094B u+0902 u+0928 u+0939 u+0940 u+0902 u+092C u+094B u+0932 u+0938 u+0915 u+0924 u+0947 u+0939 u+0948 u+0902 BRACE: 2b7xtenqdr7zc6uma2pmcz7ibage237kdemicnk9gei32 RACE: bextsmslc44t6kcnezabktjpjmbcqokaaiwewmrycuseookiai LACE: dyes6ojsjmltspzijuteafknf5fqekbziabcyszshaksirzzjaba AMC-O: ajeurvjvcmthvjvruipugatfpurmscuivjascunmvcvitfuehvjisc AMC-M: ajhurbvcwmthbhuiwpugitfwpurwmscuibiscunwmvcatfuerbwisc AMC-R: 3urvjvcwmthjruiwpugwatfwpurmscuivjascunmvcvitfuewhjwisc AMC-V: 3urvjvcwmthjruiwpugwatfwpurwmscuivjiscunwmkvitfuewhvjwi\ sc ADUDE: 3wrtgmzjxnuqgthyfymygxfxiycyewjuktbzjwcuqyhzjkupvbydzqz\ bwk AMC-W: 3urvjcwmthvjruiwpugwatfwpurwmscuivjwascunwmvcitfuewhvjw\ isc UTF-16: ???????????????????????????????????????????????????????\ ????? UTF-8: ???????????????????????????????????????????????????????\ ??????????????????????????????????? (F) Japanese (kanji and hiragana): u+306A u+305C u+307F u+3093 u+306A u+65E5 u+672C u+8A9E u+3092 u+8A71 u+3057 u+3066 u+304F u+308C u+306A u+3044 u+306E u+304B UTF-16: ???????????????????????????????????? BRACE: ji8nr5zj8uqth7v97mjchakwcg7dqemw88nj5gbe AMC-O: gvagkxnzr3dkx8fzun243q3c24zbxhgwr2nkweqwm AMC-R: vsykxnzr3dkyx8fyzun243q3c24zbxhgwr2nkweqwm AMC-V: vsykxnzr3dykb9fcjnme83cmdtxhygwr2nykweyqwm AMC-M: bsnkxnzr3dkyx8fyzun243q3c24zbxhgwr2nkweqwm AMC-W: vsykxnzr3dykyx8fcjnme8vs3cmdtvsxhygwr2nykweyqwm ADUDE: vsskvgud8n9jxx2ru6j875c54sn548d54ugvbuj6d8guqukuf LACE: auyguxd7snvaczpfaftsyamktyatbeqbrjyqqmcxmzhyy2senzfq UTF-8: ?????????????????????????????????????????????????????? RACE: 3aygumc4gb7tbezqnjs6kzzmrkpdbeukoeyfomdggbhtbdbqniyeimd\ ogbfq (G) Korean (Hangul syllables): u+C138 u+ACC4 u+C758 u+BAA8 u+B4E0 u+C0AC u+B78C u+B4E4 u+C774 u+D55C u+AD6D u+C5B4 u+B97C u+C774 u+D574 u+D55C u+B2E4 u+BA74 u+C5BC u+B9C8 u+B098 u+C88B u+C744 u+AE4C UTF-16: ???????????????????????????????????????????????? UTF-8: ???????????????????????????????????????????????????????\ ????????????????? AMC-M: yhxcj2w6exiaxi68acfn92n68ezehk6xypdpwam6zehmwhk648eavwd\ p6aqi23ieemweywn AMC-V: 6tvifgem42ixihhakfnh6nhhem5wrk6fmpmpwim6zermwrk6gzeivwm\ p6iqige2nemm4efun AMC-W: 6tvifgem42ixihhakfnh6nhhem5wrk6fmpmpwim6m5wrmwxn5u8eivw\ mp6iqige2nemm4efun BRACE: y394qebjusrcndbs82pkvstf96sxufcr7ffr4vbgdwsxufcx8pdktgb\ gmnsqydmk7im56arju6pt82 LACE: 77atrlgey5mlvkfu4dakzn4mwtsmo5gvlsww3rnuxf6mo5gvotkvzmx\ exj2mlpfzzcyjrsely5ck4ta RACE: 3datrlgey5mlvkfu4dakzn4mwtsmo5gvlsww3rnuxf6mo5gvotkvzmx\ exj2mlpfzzcyjrsely5ck4ta AMC-O: m6hwq6tvi466exi44ia6s4nz2neze7xxn47yp6x5e3znze7xze7xxnu\ 8e4ze6x5n36is3i622mwe48wn ADUDE: 6txiy79ny53nz79a8wizwwnzzuavyizv3atuuiz2vby27jz66iz8sit\ usauiyz5i23az96iz6ze3xaz2td96ry3si AMC-R: 6tvi466ezxi544i5w8a6s4nz2nw8e6zze7xxn47yp6x5e53znze7xze\ 7xxn5u8e54ze6x5n36is3i622m6zwe48wn (H) Russian (Cyrillic): U+043F u+043E u+0447 u+0435 u+043C u+0443 u+0436 u+0435 u+043E u+043D u+0438 u+043D u+0435 u+0433 u+043E u+0432 u+043E u+0440 u+044F u+0442 u+043F u+043E u+0440 u+0443 u+0441 u+0441 u+043A u+0438 ADUDE: wxRbzjzcjzrzfdmdffigpnnzqrpzpbzqdcazmc AMC-W: wvRqwhvfnwdvgfqpipfdqcqwarcvrqwadbbvki AMC-M: aehHgrvfemvgvfgfafvfvdgvcgiwrkhgimjjca AMC-V: wvRgrvfnmvgfqpipfdqcqwawrwcrqwawdwbwbka AMC-R: wvRqwhfnwdgfqpipfdqcqwawrcvrvqwawdbbvkvi AMC-O: aedRqwhfnwdgfqpipfdqcqwawrwcrqwawdwbwbki BRACE: 269xyjvcyafqfdwyr3xfd8z8byi6z39xyi692s7ug2 RACE: aq7t4rzvhrbtmnj6hu4d2njthyzd4qcpii7t4qcdifatuoa LACE: dqcd6pshgu6egnrvhy6tqpjvgm7depsaj5bd6psainaucory UTF-16: ???????????????????????????????????????????????????????\ ??? UTF-8: ??????????????????????????????????????????????????????? ??? (I) Spanish: Porqu<eacute>nopuedensimplementehablarenEspa<ntilde>ol U+0050 u+006F u+0072 u+0071 u+0075 u+00E9 u+006E u+006F u+0070 u+0075 u+0065 u+0064 u+0065 u+006E u+0073 u+0069 u+006D u+0070 u+006C u+0065 u+006D u+0065 u+006E u+0074 u+0065 u+0068 u+0061 u+0062 u+006C u+0061 u+0072 u+0065 u+006E U+0045 u+0073 u+0070 u+0061 u+00F1 u+006F u+006C UTF-8: Porqu??nopuedensimplementehablarenEspa??ol AMC-V: -Porqu-j-nopuedensimplementehablarenEspa-j-ol AMC-W: -Porqu-j-nopuedensimplementehablarenEspa-xb-ol AMC-R: -Porqu-j-nopuedensimplementehablarenEspa-9b-ol AMC-M: aa7-Porqu-b-nopuedensimplementehablarenEspa-j-ol BRACE: 22x-Porqu-9-nopuedensimplementehablarenEspa-j-ol AMC-O: aaq-Porqu-j-nopuedensimplementehablarenEspa-9b-ol ADUDE: tAtrtpde3n2hbtrftabbmtptketptnjiimtktbpjdqptdthmMtgdtb3\ a3qd RACE: abyg64troxuw433qovswizloonuw24dmmvwwk3tumvugcytmmfzgk3t\ fonygd4lpnq LACE: faaha33sof26s3tpob2wkzdfnzzws3lqnrsw2zloorswqylcnrqxezl\ omvzxayprn5wa UTF-16: ???????????????????????????????????????????????????????\ ????????????????????????? (J) Taiwanese: u+4ED6 u+5011 u+7232 u+4EC0 u+9EBD u+4E0D u+8AAA u+4E2D u+6587 UTF-16: ?????????????????? UTF-8: ??????????????????????????? AMC-M: uqk7gstbetu6arx7spkxkupbnh BRACE: kgcqui49gatc2wyrn8y7cndgte9 AMC-V: w87gutbfbus6a385psspmfkupb6h AMC-W: w87gutbfbus6a385psspmfksupb6h AMC-R: w87gxstbzuvc6a385psp244kupyx2h AMC-O: eqpgxstbzuvc6a385psp244kupyx2h RACE: 3bhnmuaroize5qe6xvha3cvkjywwlby LACE: 75hnmuaroize5qe6xvha3cvkjywwlby ADUDE: w85gt86huuudv69c7szp7s5a6w4h6w2hu54k (K) Vietnamese: Ta<dotbelow>isaoho<dotbelow>kh<ocirc>ngth<ecirc><hookabove>chi\ <hookabove>no<acute>iti<ecirc><acute>ngVi<ecirc><dotbelow>t U+0054 u+0061 u+0323 u+0069 u+0073 u+0061 u+006F u+0068 u+006F u+0323 u+006B u+0068 u+00F4 u+006E u+0067 u+0074 u+0068 u+00EA u+0309 u+0063 u+0068 u+0069 u+0309 u+006E u+006F u+0301 u+0069 u+0074 u+0069 u+00EA u+0301 u+006E u+0067 U+0056 u+0069 u+00EA u+0323 u+0074 UTF-8: Ta??isaoho??kh??ngth????chi??no??iti????ngVi????t AMC-V: -Ta-vud-isaoho-d-kh-s9e-ngth-s8ksj-chi-sj-no-sb-iti-csb\ -ngVi-cud-t AMC-O: aava-Ta-vud-isaoho-vud-kh-9e-ngth-8kj-chi-j-no-b-iti-8k\ b-ngVi-8kvud-t AMC-M: ada-Ta-ud-isaoho-ud-kh-s9e-ngth-s8kj-chi-j-no-b-iti-s8k\ b-ngVi-s8kud-t AMC-R: -Ta-vud-isaoho-d-kh-s9e-ngth-s8kvsj-chi-vsj-no-b-iti-s8\ kb-ngVi-s8kud-t AMC-W: -Ta-vud-isaoho-d-kh-s9e-ngth-wkvsj-chi-j-no-b-iti-s8kvs\ b-ngVi-s8kvud-t BRACE: i54-Ta-8-isaoho-ay-kh-29n-ngth-s2xa6i-chi-k-no-2g-iti-2\ 9c29-ngVi-25p48-t UTF-16: ???????????????????????????????????????????????????????\ ????????????????????? ADUDE: tEtfvwcvwktktcqhhvwnvwid3n3kjtdtn2cv8dvykmbvyavyhbvyqvy\ itptp2dv8mvyrjtBtr2dv6jvxh LACE: aiahiyibamrqmadjonqw62dpaebsgcaannupi3thoruouaidbebqay3\ ineaqgcicabxg6aidaecaa2lunhvacaybauag4z3wnhvacazdaeahi RACE: ap7xj73bep7wt73t75q76377nd7w6i77np7wr77u75xp6z77ot7wr77\ kbh7wh73i75uqt73o75xqd73j752p62p75ia763x7m77xn73j77vch7\ 3u The next several examples are all names of Japanese music artists, song titles, and TV programs, just because the author happens to have them handy (but Japanese is useful for providing examples of single-row text, two-row text, ideographic text, and various mixtures thereof). (L) 3<nen>B<gumi><kinpachi><sensei> u+0033 u+5E74 U+0042 u+7D44 u+91D1 u+516B u+5148 u+751F UTF-16: ???????????????? UTF-8: 3???B??????????????? AMC-V: -3-x8ze-B-h4en8tvymwif29 AMC-W: -3-x8ze-B-h4en8tvymwizxtr AMC-M: utk-3-8ze-B-hkenqtymwifi9 BRACE: u-3-ygj-b-ynb6gjc7pp4k5p5w AMC-O: fb8h-3-e-B-z7we3t7bymwizxtr ADUDE: xdx8whx8tGz7ug863f6s5kuduwxh RACE: 3aadgxtuabrh2rer2fiwwukioupq LACE: 74adgxtuabrh2rer2fiwwukioupq AMC-R: -3-x8ze-B-z7we3t7btymtwizxtr (M) <amuro><namie>-with-SUPER-MONKEYS u+5B89 u+5BA4 u+5948 u+7F8E u+6075 u+002D u+0077 u+0069 u+0074 u+0068 u+002D U+0053 U+0055 U+0050 U+0045 U+0052 u+002D U+004D U+004F U+004E U+004B U+0045 U+0059 U+0053 UTF-8: ??????????????????-with-SUPER-MONKEYS AMC-V: x52j4e5wiinqavx---with--SUPER--MONKEYS AMC-W: x52j4e5wiz92qavx---with--SUPER--MONKEYS AMC-M: u5m2j4etwif6q2zf---with--SUPER--MONKEYS AMC-R: x52j4e3wiz92qyszf---with--SUPER--MONKEYS AMC-O: fmij4e3wiz92qyszf---with--SUPER--MONKEYS BRACE: uvj7fuaqcahy982xa---with--SUPER--MONKEYS ADUDE: x58jupu8nuy6gt99m-yssctqtptn-tMGFtFtH-tRCBFQtNK UTF-16: ???????????????????????????????????????????????? LACE: ajnytjablfeac74oafqhkeyafv3ws5difvzxk4dfoiww233onnsxs4y RACE: 3bnysw5elfeh7dtaouac2adxabuqa5aanaac2adtab2qa4aamuaheab\ nabwqa3yanyagwadfab4qa4y (N) Hello-Another-Way-<sorezore><no><basho> U+0048 u+0065 u+006C u+006C u+006F u+002D U+0041 u+006E u+006F u+0074 u+0068 u+0065 u+0072 u+002D U+0057 u+0061 u+0079 u+002D u+305D u+308C u+305E u+308C u+306E u+5834 u+6240 UTF-8: Hello-Another-Way-????????????????????? AMC-V: -Hello--Another--Way---vsxp2nxq2nyq4vebca BRACE: ji7-Hello--Another--Way---v3jhaefvd2ufj62 AMC-R: -Hello--Another--Way---vsxp2nq2nyqx2veyuwa AMC-W: -Hello--Another--Way---vsxp2nxq2nyq4veyuwa AMC-O: daf-Hello--Another--Way---p2nq2nyqx2veyuwa AMC-M: bsk-Hello--Another--Way---p2nq2nyqx2veyuwa ADUDE: Ipjad-Qrbtmtnpth-Ftgti-vsue7b7c7c8cy2xkv4ze UTF-16: ?????????????????????????????????????????????????? LACE: ciagqzlmnrxs2ylon52gqzlsfv3wc6jnauyf3dc6rrxacwbuafrea RACE: 3aagqadfabwaa3aan4ac2adbabxaa3yaoqagqadfabzaaliao4agcad\ zaawtaxjqrqyf4memgbxfqndcia (O) <hitotsu><yane><no><shita>2 u+3072 u+3068 u+3064 u+5C4B u+6839 u+306E u+4E0B u+0032 UTF-16: ???????????????? AMC-V: vszcyiye8wmct3yqssm-2 UTF-8: ?????????????????????2 AMC-O: dagzciex6wmy2vjqw8sm-2 AMC-M: bsnzciex6wmy2vjqw8sm-2 BRACE: ji96u56uwbhf2wqxnw4s-2 AMC-R: vszcyiyex6wmy2vjqw8sm-2 AMC-W: vszcyie8wmy2vjvsyqssm-2 ADUDE: vstctkny6urvwzcx2xhz8yfw8vj RACE: 3ayhemdigbsfys3iheyg4tqlaaza LACE: 74yhemdigbsfys3iheyg4tqlaaza (P) Maji<de>Koi<suru>5<byou><mae> U+004D u+0061 u+006A u+0069 u+3067 U+004B u+006F u+0069 u+3059 u+308B u+0035 u+79D2 u+524D UTF-8: Maji???Koi??????5?????? UTF-16: ?????????????????????????? AMC-V: -Maji-vsyh-Koi-xj2m-5-g8uwwp AMC-W: -Maji-vsyh-Koi-xj2m-5-z37cwwp AMC-M: bsm-Maji-r-Koi-b2m-5-z37cxuwp BRACE: ji8-Maji-g-Koi-qe7x-5-wx7p6ma AMC-R: -Maji-vsyh-Koi-xj2m-5-z37cxuwp AMC-O: dag-Maji-h-Koi-xj2m-5-z37cxuwp ADUDE: PnmdvssqvssNegvsva7cvs5qz38hu53r RACE: 3aag2adbabvaa2jqm4agwadpabutawjqrmadk6oskjgq LACE: 74ag2adbabvaa2jqm4agwadpabutawjqrmadk6oskjgq (Q) <pafii>de<runba> u+30D1 u+30D5 u+30A3 u+30FC u+0064 u+0065 u+30EB u+30F3 u+30D0 UTF-16: ?????????????? BRACE: 3iu8pazt-de-pygi AMC-O: dapbf4d9n-de-8m9da AMC-M: bs3jp4d9n-de-8m9di AMC-R: vs7bf4d9n-de-8m9d7a AMC-W: vs7b7f4d9n-de-8m9d7a RACE: gdi5li7475sp6zpl6pia AMC-V: vs7b7f4d9n-de-8m9d7a ADUDE: vs5bezgxrvs3ibvs2qtiud UTF-8: ????????????de????????? LACE: aqyndvnd7qbaazdfamyox46q (R) <sono><supiido><de> u+305D u+306E u+30B9 u+30D4 u+30FC u+30C9 u+3067 RACE: gbow5oou7tewo UTF-16: ?????????????? BRACE: bidprdmp9wt7mi LACE: a4yf23vz2t6mszy AMC-O: dagxpq5j7e9n6jh AMC-M: bsmfyq5j7e9n6jr ADUDE: vsvpvd7hypuivf4q AMC-R: vsxpyq5j7e9n6jyh AMC-W: vsxpyq5j7e9n6jyh AMC-V: vsxpyq5j7e9n6jyh UTF-8: ????????????????????? The last example is an ASCII string that breaks not only the existing rules for host name labels but also the rules proposed in [NAMEPREP03] for internationalized domain names. (S) -> $1.00 <- u+002D u+003E u+0020 u+0024 u+0031 u+002E u+0030 u+0030 u+0020 u+003C u+002D UTF-8: -> $1.00 <- ADUDE: -xqtqetftrtqatatn- RACE: aawt4ibegexdambahqwq LACE: bmac2praeqys4mbqea6c2 AMC-W: --svquae-1-q-00-avn-- AMC-V: --svquae-1-q-00-avn-- UTF-16: ?????????????????????? AMC-R: --svquaue-1-q-00-avn-- AMC-O: aac--vqae-1-q-00-avn-- AMC-M: aae--vqae-1-q-00-avn-- BRACE: 229--t2b4-1-w-00-i9i-- Security considerations Users expect each domain name in DNS to be controlled by a single authority. If a Unicode string intended for use as a domain label could map to multiple ACE labels, then an internationalized domain name could map to multiple ACE domain names, each controlled by a different authority, some of which could be spoofs that hijack service requests intended for another. Therefore AMC-ACE-W is designed so that each Unicode string has a unique encoding. However, there can still be multiple Unicode representations of the "same" text, for various definitions of "same". This problem is addressed to some extent by the Unicode standard under the topic of canonicalization, and this work is leveraged for domain names by "nameprep" [NAMEPREP03]. Acknowledgements AMC-ACE-W reuses a number of preexisting techniques. The basic encoding of integers to quartets to quintets to base-32 comes from UTF-5 [UTF5], and the particular variant used here comes from AMC-ACE-M [AMCACEM], as does the "wide style" (style 1). The idea of avoiding 0, 1, o, and l in base-32 strings was taken from SFS [SFS]. The idea of encoding deltas from reference points was taken from RACE (of which the latest version is [RACE03]), which may have gotten the idea from Unicode Technical Standard #6 [UTS6]. The idea of switching between literal mode and base-32 mode comes from BRACE [BRACE]. The general idea of using the alphabetic case of base-32 characters to indicate the desired case of the Unicode characters was suggested by this author, and first applied to the UTF-5-style encoding in DUDE (of which the latest version is [DUDE01]). The heuristic used to adapt the style is similar to the one used in AMC-ACE-V. The heuristic used to adapt the reference points is similar to the one used by DUDE. References [AltDUDE] Adam Costello, "AltDUDE version 0.0.3", 2001-May-27, update of draft-ietf-idn-altdude-00, latest version at http://www.cs.berkeley.edu/~amc/charset/altdude. [AMCACEM] Adam Costello, "AMC-ACE-M version 0.1.4", 2001-Apr-01, update of draft-ietf-idn-amc-ace-m-00, latest version at http://www.cs.berkeley.edu/~amc/charset/amc-ace-m. [AMCACEO] Adam Costello, "AMC-ACE-O version 0.0.5", 2001-May-27, update of draft-ietf-idn-amc-ace-o-00, latest version at http://www.cs.berkeley.edu/~amc/charset/amc-ace-o. [AMCACER] Adam Costello, "AMC-ACE-R version 0.2.1", 2001-May-31, draft-ietf-idn-amc-ace-r-01, latest version at http://www.cs.berkeley.edu/~amc/charset/amc-ace-r. [AMCACEV] Adam Costello, "AMC-ACE-V version 0.1.0", 2001-May-31, draft-ietf-idn-amc-ace-v-00, latest version at http://www.cs.berkeley.edu/~amc/charset/amc-ace-v. [BRACE] Adam Costello, "BRACE: Bi-mode Row-based ASCII-Compatible Encoding for IDN version 0.1.2", 2000-Sep-19, draft-ietf-idn-brace-00, version at http://www.cs.berkeley.edu/~amc/charset/brace. [DUDE01] Mark Welter, Brian Spolarich, "DUDE: Differential Unicode Domain Encoding", 2001-Mar-02, draft-ietf-idn-dude-01. [IDN] Internationalized Domain Names (IETF working group), http://www.i-d-n.net/, idn@ops.ietf.org. [IDNA] Patrik Faltstrom, Paul Hoffman, "Internationalizing Host Names In Applications (IDNA)", draft-ietf-idn-idna-01. [NAMEPREP03] Paul Hoffman, Marc Blanchet, "Preparation of Internationalized Host Names", 2001-Feb-24, draft-ietf-idn-nameprep-03. [PROVINCIAL] Michael Kaplan, "The 'anyone can be provincial!' page", http://www.trigeminal.com/samples/provincial.html. [RACE03] Paul Hoffman, "RACE: Row-based ASCII Compatible Encoding for IDN", 2000-Nov-28, draft-ietf-idn-race-03. [RFC952] K. Harrenstien, M. Stahl, E. Feinler, "DOD Internet Host Table Specification", 1985-Oct, RFC 952. [RFC1034] P. Mockapetris, "Domain Names - Concepts and Facilities", 1987-Nov, RFC 1034. [SFS] David Mazieres et al, "Self-certifying File System", http://www.fs.net/. [UNICODE] The Unicode Consortium, "The Unicode Standard", http://www.unicode.org/unicode/standard/standard.html. [UTF5] James Seng, Martin Duerst, Tin Wee Tan, "UTF-5, a Transformation Format of Unicode and ISO 10646", draft-jseng-utf5-*. [UTS6] Misha Wolf, Ken Whistler, Charles Wicksteed, Mark Davis, Asmus Freytag, "Unicode Technical Standard #6: A Standard Compression Scheme for Unicode", http://www.unicode.org/unicode/reports/tr6/. Author Adam M. Costello <amc@cs.berkeley.edu> http://www.cs.berkeley.edu/~amc/ Example implementation /******************************************/ /* amc-ace-w.c 0.1.0 (2001-May-31-Thu) */ /* Adam M. Costello <amc@cs.berkeley.edu> */ /******************************************/ /* This is ANSI C code (C89) implementing AMC-ACE-W version 0.1.*. */ /************************************************************/ /* Public interface (would normally go in its own .h file): */ #include <limits.h> enum amc_ace_status { amc_ace_success, amc_ace_bad_input, amc_ace_big_output /* Output would exceed the space provided. */ }; enum case_sensitivity { case_sensitive, case_insensitive }; #if UINT_MAX >= 0x1FFFFF typedef unsigned int u_code_point; #else typedef unsigned long u_code_point; #endif enum amc_ace_status amc_ace_w_encode( unsigned int input_length, const u_code_point input[], const unsigned char uppercase_flags[], unsigned int *output_size, char output[] ); /* amc_ace_w_encode() converts Unicode to AMC-ACE-W (without */ /* any signature). The input must be represented as an array */ /* of Unicode code points (not code units; surrogate pairs */ /* are not allowed), and the output will be represented as */ /* null-terminated ASCII. The input_length is the number of */ /* code points in the input. The output_size is an in/out */ /* argument: the caller must pass in the maximum number of */ /* characters that may be output (including the terminating */ /* null), and on successful return it will contain the number of */ /* characters actually output (including the terminating null, */ /* so it will be one more than strlen() would return, which is */ /* why it is called output_size rather than output_length). The */ /* uppercase_flags array must hold input_length boolean values, */ /* where nonzero means the corresponding Unicode character should */ /* be forced to uppercase after being decoded, and zero means it */ /* is caseless or should be forced to lowercase. Alternatively, */ /* uppercase_flags may be a null pointer, which is equivalent */ /* to all zeros. The letters a-z and A-Z are always encoded */ /* literally, regardless of the corresponding flags. The encoder */ /* always outputs lowercase base-32 characters except when */ /* nonzero values of uppercase_flags require otherwise. The */ /* return value may be any of the amc_ace_status values defined */ /* above; if not amc_ace_success, then output_size and output may */ /* contain garbage. On success, the encoder will never need to */ /* write an output_size greater than input_length*5+1, because of */ /* how the encoding is defined. */ enum amc_ace_status amc_ace_w_decode( enum case_sensitivity case_sensitivity, char scratch_space[], const char input[], unsigned int *output_length, u_code_point output[], unsigned char uppercase_flags[] ); /* amc_ace_w_decode() converts AMC-ACE-W (without any signature) */ /* to Unicode. The input must be represented as null-terminated */ /* ASCII, and the output will be represented as an array of */ /* Unicode code points. The case_sensitivity argument influences */ /* the check on the well-formedness of the input string; it */ /* must be case_sensitive if case-sensitive comparisons are */ /* allowed on encoded strings, case_insensitive otherwise. */ /* The scratch_space must point to space at least as large */ /* as the input, which will get overwritten (this allows the */ /* decoder to avoid calling malloc()). The output_length is */ /* an in/out argument: the caller must pass in the maximum */ /* number of code points that may be output, and on successful */ /* return it will contain the actual number of code points */ /* output. The uppercase_flags array must have room for at */ /* least output_length values, or it may be a null pointer */ /* if the case information is not needed. A nonzero flag */ /* indicates that the corresponding Unicode character should */ /* be forced to uppercase by the caller, while zero means it */ /* is caseless or should be forced to lowercase. The letters */ /* a-z and A-Z are output already in the proper case, but their */ /* flags will be set appropriately so that applying the flags */ /* would be harmless. The return value may be any of the */ /* amc_ace_status values defined above; if not amc_ace_success, */ /* then output_length, output, and uppercase_flags may contain */ /* garbage. On success, the decoder will never need to write */ /* an output_length greater than the length of the input (not */ /* counting the null terminator), because of how the encoding is */ /* defined. */ /**********************************************************/ /* Implementation (would normally go in its own .c file): */ #include <string.h> /* base32[q] is the lowercase base-32 character representing */ /* the number q from the range 0 to 31. Note that we cannot */ /* use string literals for ASCII characters because an ANSI C */ /* compiler does not necessarily use ASCII. */ static const char base32[] = { 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, /* a-k */ 109, 110, /* m-n */ 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, /* p-z */ 50, 51, 52, 53, 54, 55, 56, 57 /* 2-9 */ }; /* base32_decode(c) returns the value of a base-32 character, in the */ /* range 0 to 31, or the constant base32_invalid if c is not a valid */ /* base-32 character. */ enum { base32_invalid = 32 }; static unsigned int base32_decode(char c) { if (c < 50) return base32_invalid; if (c <= 57) return c - 26; if (c < 97) c += 32; if (c < 97 || c == 108 || c == 111 || c > 122) return base32_invalid; return c - 97 - (c > 108) - (c > 111); } /* unequal(case_sensitivity,s1,s2) returns 0 if the strings s1 and s2 */ /* are equal, 1 otherwise. If case_sensitivity is case_insensitive, */ /* then ASCII A-Z are considered equal to a-z respectively. */ static int unequal( enum case_sensitivity case_sensitivity, const char s1[], const char s2[] ) { char c1, c2; if (case_sensitivity != case_insensitive) return strcmp(s1,s2) != 0; for (;;) { c1 = *s1; c2 = *s2; if (c1 >= 65 && c1 <= 90) c1 += 32; if (c2 >= 65 && c2 <= 90) c2 += 32; if (c1 != c2) return 1; if (c1 == 0) return 0; ++s1, ++s2; } } /* update(refpoint,style,n,k) updates refpoint[1..3] and *style */ /* based on n (the most recent code point) and k (the number of */ /* base-32 characters used to encode it). */ static void update( u_code_point refpoint[6], unsigned int *style, u_code_point n, unsigned int k ) { *style = k < 3 ? 0 : k > 3 ? 1 : *style; refpoint[1] = (n >> 4) << 4; if (k > 2) refpoint[2] = n - 0xA0 < 0xE0 ? 0xA0 : (n >> 8) << 8; if (k > 3) refpoint[3] = n - 0x3000 < 0x7000 ? 0x4E00 : *style == 1 && n - 0xA000 < 0x3800 ? 0x8800 : (n >> 12) << 12; } /* Main encode function: */ enum amc_ace_status amc_ace_w_encode( unsigned int input_length, const u_code_point input[], const unsigned char uppercase_flags[], unsigned int *output_size, char output[] ) { unsigned int style, literal, max_out, in, out, k, j; u_code_point n, delta; const u_code_point maxdelta[2][6] = {{0,0xF,0xFF,0xFFF,0xFFFF,0xFFFFF}, {0,0,0xFF,0x4FFF,0xFFFF,0xFFFFF}}; char shift; /* Initialize the state: */ u_code_point refpoint[6] = {0, 0xE0, 0xA0, 0, 0, 0x10000}; style = literal = 0; max_out = *output_size; for (in = out = 0; in < input_length; ++in) { /* At the start of each iteration, in and out are the number of */ /* items already input/output, or equivalently, the indices of */ /* the next items to be input/output. */ n = input[in]; /* Check the code point range to avoid array bounds errors later: */ if (n > 0x10FFFF) return amc_ace_bad_input; if (n == 0x2D) { /* Hyphen-minus is doubled. */ if (max_out - out < 2) return amc_ace_big_output; output[out++] = 0x2D; output[out++] = 0x2D; } else if ( n <= 122 && ( n >= 97 || n == 45 || (n >= 48 && n <= 57) || (n >= 65 && n <= 90) ) ) { /* Encode an LDH character literally. */ if (max_out - out < 1 + !literal) return amc_ace_big_output; /* Switch to literal mode if necessary: */ if (!literal) output[out++] = 0x2D; literal = 1; output[out++] = n; } else { /* Encode a non-LDH character using base-32. */ /* First compute the number of base-32 characters (k): */ for (k = 1 + style; ; ++k) { delta = n - refpoint[k]; if (delta <= maxdelta[style][k]) break; } if (max_out - out < k + literal) return amc_ace_big_output; /* Switch to base-32 mode if necessary: */ if (literal) output[out++] = 0x2D; literal = 0; shift = uppercase_flags && uppercase_flags[in] ? 32 : 0; /* Check for the extended delta of style 1 window 3: */ if (k == 3 && delta >= 0x1000) { /* The top 16k of window 3 is encoded as 0xxxx xxxxx xxxxx. */ delta -= 0x1000; output[out++] = base32[delta >> 10] - shift; output[out++] = base32[(delta >> 5) & 0x1F]; output[out++] = base32[delta & 0x1F]; } else { /* Each quintet has the form 1xxxx except the last is 0xxxx. */ /* Computing the base-32 digits in reverse order is easiest. */ out += k; output[out - 1] = base32[delta & 0xF] - shift; for (j = 2; j <= k; ++j) { delta >>= 4; output[out - j] = base32[0x10 | (delta & 0xF)]; } } update(refpoint, &style, n, k); } } /* Append the null terminator: */ if (max_out - out < 1) return amc_ace_big_output; output[out++] = 0; *output_size = out; return amc_ace_success; } /* Main decode function: */ enum amc_ace_status amc_ace_w_decode( enum case_sensitivity case_sensitivity, char scratch_space[], const char input[], unsigned int *output_length, u_code_point output[], unsigned char uppercase_flags[] ) { u_code_point q, delta; char c; unsigned int style, literal, max_out, in, out, k, scratch_size; enum amc_ace_status status; /* Initialize the state: */ u_code_point refpoint[6] = {0, 0xE0, 0xA0, 0, 0, 0x10000}; style = literal = 0; max_out = *output_length; for (c = input[in = 0], out = 0; c != 0; c = input[++in], ++out) { /* At the start of each iteration, in and out are the number of */ /* items already input/output, or equivalently, the indices of */ /* the next items to be input/output. c is the same as input[in] */ /* except when "extra" characters have been consumed (see below). */ if (c == 0x2D && input[in + 1] != 0x2D) { /* Unpaired hyphen-minus toggles mode. */ literal = !literal; c = input[++in]; } if (max_out - out < 1) return amc_ace_big_output; if (c == 0x2D) { /* Double hyphen-minus represents a hyphen-minus. */ ++in; output[out] = 0x2D; } else { if (literal) output[out] = c; else { /* Decode a base-32 sequence. */ /* First decode quintets until 0xxxx is found: */ for (delta = 0, k = 1; ; c = input[++in], ++k) { q = base32_decode(c); if (q == base32_invalid || k > 5) return amc_ace_bad_input; delta = (delta << 4) | (q & 0xF); if (q >> 4 == 0) break; } if (style == 1 && k == 1) { /* Style 1 has no window 1, so it must be the extended */ /* delta of window 3, encoded as 0xxxx xxxxx xxxxx. */ /* Consume the two "extra" characters: */ for (; k < 3; ++k) { q = base32_decode(input[++in]); if (q == base32_invalid) return amc_ace_bad_input; delta = (delta << 5) | q; } delta += 0x1000; } output[out] = refpoint[k] + delta; update(refpoint, &style, output[out], k); } } /* Case of last non-extra character determines uppercase flag: */ if (uppercase_flags) uppercase_flags[out] = c >= 65 && c <= 90; } /* Enforce the uniqueness of the encoding by re-encoding */ /* the output and comparing the result to the input: */ scratch_size = ++in; status = amc_ace_w_encode(out, output, uppercase_flags, &scratch_size, scratch_space); if (status != amc_ace_success || scratch_size != in || unequal(case_sensitivity, scratch_space, input) ) return amc_ace_bad_input; *output_length = out; return amc_ace_success; } /******************************************************************/ /* Wrapper for testing (would normally go in a separate .c file): */ #include <assert.h> #include <stdio.h> #include <stdlib.h> #include <string.h> /* For testing, we'll just set some compile-time limits rather than */ /* use malloc(), and set a compile-time option rather than using a */ /* command-line option. */ enum { unicode_max_length = 256, ace_max_size = 256, test_case_sensitivity = case_insensitive /* suitable for host names */ }; static void usage(char **argv) { fprintf(stderr, "%s -e reads code points and writes an AMC-ACE-W string.\n" "%s -d reads an AMC-ACE-W string and writes code points.\n" "Input and output are plain text in the native character set.\n" "Code points are in the form u+hex separated by whitespace.\n" "An AMC-ACE-W string is a newline-terminated sequence of LDH\n" "characters (without any signature).\n" "The case of the u in u+hex is the force-to-uppercase flag.\n" , argv[0], argv[0]); exit(EXIT_FAILURE); } static void fail(const char *msg) { fputs(msg,stderr); exit(EXIT_FAILURE); } static const char too_big[] = "input or output is too large, recompile with larger limits\n"; static const char invalid_input[] = "invalid input\n"; static const char io_error[] = "I/O error\n"; /* The following string is used to convert LDH */ /* characters between ASCII and the native charset: */ static const char ldh_ascii[] = "................" "................" ".............-.." "0123456789......" ".ABCDEFGHIJKLMNO" "PQRSTUVWXYZ....." ".abcdefghijklmno" "pqrstuvwxyz"; int main(int argc, char **argv) { enum amc_ace_status status; int r; char *p; if (argc != 2) usage(argv); if (argv[1][0] != '-') usage(argv); if (argv[1][2] != 0) usage(argv); if (argv[1][1] == 'e') { u_code_point input[unicode_max_length]; unsigned long codept; unsigned char uppercase_flags[unicode_max_length]; char output[ace_max_size], uplus[3]; unsigned int input_length, output_size, i; /* Read the input code points: */ input_length = 0; for (;;) { r = scanf("%2s%lx", uplus, &codept); if (ferror(stdin)) fail(io_error); if (r == EOF || r == 0) break; if (r != 2 || uplus[1] != '+' || codept > (u_code_point)-1) { fail(invalid_input); } if (input_length == unicode_max_length) fail(too_big); if (uplus[0] == 'u') uppercase_flags[input_length] = 0; else if (uplus[0] == 'U') uppercase_flags[input_length] = 1; else fail(invalid_input); input[input_length++] = codept; } /* Encode: */ output_size = ace_max_size; status = amc_ace_w_encode(input_length, input, uppercase_flags, &output_size, output); if (status == amc_ace_bad_input) fail(invalid_input); if (status == amc_ace_big_output) fail(too_big); assert(status == amc_ace_success); /* Convert to native charset and output: */ for (p = output; *p != 0; ++p) { i = *p; assert(i <= 122 && ldh_ascii[i] != '.'); *p = ldh_ascii[i]; } r = puts(output); if (r == EOF) fail(io_error); return EXIT_SUCCESS; } if (argv[1][1] == 'd') { char input[ace_max_size], scratch[ace_max_size], *pp; u_code_point output[unicode_max_length]; unsigned char uppercase_flags[unicode_max_length]; unsigned int input_length, output_length, i; /* Read the AMC-ACE-W input string and convert to ASCII: */ fgets(input, ace_max_size, stdin); if (ferror(stdin)) fail(io_error); if (feof(stdin)) fail(invalid_input); input_length = strlen(input); if (input[input_length - 1] != '\n') fail(too_big); input[--input_length] = 0; for (p = input; *p != 0; ++p) { pp = strchr(ldh_ascii, *p); if (pp == 0) fail(invalid_input); *p = pp - ldh_ascii; } /* Decode: */ output_length = unicode_max_length; status = amc_ace_w_decode(test_case_sensitivity, scratch, input, &output_length, output, uppercase_flags); if (status == amc_ace_bad_input) fail(invalid_input); if (status == amc_ace_big_output) fail(too_big); assert(status == amc_ace_success); /* Output the result: */ for (i = 0; i < output_length; ++i) { r = printf("%s+%04lX\n", uppercase_flags[i] ? "U" : "u", (unsigned long) output[i] ); if (r < 0) fail(io_error); } return EXIT_SUCCESS; } usage(argv); return EXIT_SUCCESS; /* not reached, but quiets compiler warning */ } INTERNET-DRAFT expires 2001-Nov-30
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