diff options
Diffstat (limited to 'ext/pcre/pcrelib/HACKING')
| -rw-r--r-- | ext/pcre/pcrelib/HACKING | 35 |
1 files changed, 20 insertions, 15 deletions
diff --git a/ext/pcre/pcrelib/HACKING b/ext/pcre/pcrelib/HACKING index 87b88191a..a90ddf879 100644 --- a/ext/pcre/pcrelib/HACKING +++ b/ext/pcre/pcrelib/HACKING @@ -49,16 +49,17 @@ complexity in Perl regular expressions, I couldn't do this. In any case, a first pass through the pattern is helpful for other reasons. -Support for 16-bit data strings -------------------------------- +Support for 16-bit and 32-bit data strings +------------------------------------------- -From release 8.30, PCRE supports 16-bit as well as 8-bit data strings, by being -compilable in either 8-bit or 16-bit modes, or both. Thus, two different -libraries can be created. In the description that follows, the word "short" is +From release 8.30, PCRE supports 16-bit as well as 8-bit data strings; and from +release 8.32, PCRE supports 32-bit data strings. The library can be compiled +in any combination of 8-bit, 16-bit or 32-bit modes, creating different +libraries. In the description that follows, the word "short" is used for a 16-bit data quantity, and the word "unit" is used for a quantity -that is a byte in 8-bit mode and a short in 16-bit mode. However, so as not to -over-complicate the text, the names of PCRE functions are given in 8-bit form -only. +that is a byte in 8-bit mode, a short in 16-bit mode and a 32-bit unsigned +integer in 32-bit mode. However, so as not to over-complicate the text, the +names of PCRE functions are given in 8-bit form only. Computing the memory requirement: how it was @@ -138,9 +139,10 @@ Format of compiled patterns --------------------------- The compiled form of a pattern is a vector of units (bytes in 8-bit mode, or -shorts in 16-bit mode), containing items of variable length. The first unit in -an item contains an opcode, and the length of the item is either implicit in -the opcode or contained in the data that follows it. +shorts in 16-bit mode, 32-bit unsigned integers in 32-bit mode), containing +items of variable length. The first unit in an item contains an opcode, and +the length of the item is either implicit in the opcode or contained in the +data that follows it. In many cases listed below, LINK_SIZE data values are specified for offsets within the compiled pattern. LINK_SIZE always specifies a number of bytes. The @@ -207,7 +209,8 @@ Matching literal characters The OP_CHAR opcode is followed by a single character that is to be matched casefully. For caseless matching, OP_CHARI is used. In UTF-8 or UTF-16 modes, -the character may be more than one unit long. +the character may be more than one unit long. In UTF-32 mode, characters +are always exactly one unit long. Repeating single characters @@ -228,7 +231,8 @@ following opcodes, which come in caseful and caseless versions: OP_POSQUERY OP_POSQUERYI Each opcode is followed by the character that is to be repeated. In ASCII mode, -these are two-unit items; in UTF-8 or UTF-16 modes, the length is variable. +these are two-unit items; in UTF-8 or UTF-16 modes, the length is variable; in +UTF-32 mode these are one-unit items. Those with "MIN" in their names are the minimizing versions. Those with "POS" in their names are possessive versions. Other repeats make use of these opcodes: @@ -299,7 +303,7 @@ bit map containing a 1 bit for every character that is acceptable. The bits are counted from the least significant end of each unit. In caseless mode, bits for both cases are set. -The reason for having both OP_CLASS and OP_NCLASS is so that, in UTF-8/16 mode, +The reason for having both OP_CLASS and OP_NCLASS is so that, in UTF-8/16/32 mode, subject characters with values greater than 255 can be handled correctly. For OP_CLASS they do not match, whereas for OP_NCLASS they do. @@ -412,7 +416,8 @@ OP_ASSERTBACK and OP_ASSERTBACK_NOT, and the first opcode inside the assertion is OP_REVERSE, followed by a two byte (one short) count of the number of characters to move back the pointer in the subject string. In ASCII mode, the count is a number of units, but in UTF-8/16 mode each character may occupy more -than one unit. A separate count is present in each alternative of a lookbehind +than one unit; in UTF-32 mode each character occupies exactly one unit. +A separate count is present in each alternative of a lookbehind assertion, allowing them to have different fixed lengths. |