libpsl/src/lookup_string_in_fixed_set.c

286 lines
7.8 KiB
C

/* Copyright 2015 The Chromium Authors. All rights reserved.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE.chromium file.
*
* Converted to C89 2015 by Tim Rühsen
*/
#include <stddef.h>
#if defined(__GNUC__) && defined(__GNUC_MINOR__)
# define _GCC_VERSION_AT_LEAST(major, minor) ((__GNUC__ > (major)) || (__GNUC__ == (major) && __GNUC_MINOR__ >= (minor)))
#else
# define _GCC_VERSION_AT_LEAST(major, minor) 0
#endif
#if _GCC_VERSION_AT_LEAST(4,0)
# define _HIDDEN __attribute__ ((visibility ("hidden")))
#else
# define _HIDDEN
#endif
#define CHECK_LT(a, b) if ((a) >= b) return 0
static const char multibyte_length_table[16] = {
0, 0, 0, 0, /* 0x00-0x3F */
0, 0, 0, 0, /* 0x40-0x7F */
0, 0, 0, 0, /* 0x80-0xBF */
2, 2, 3, 4, /* 0xC0-0xFF */
};
/**
* Get lenght of multibyte character sequence starting at a given byte.
* Returns zero if the byte is not a valid leading byte in UTF-8.
*/
static int GetMultibyteLength(char c) {
return multibyte_length_table[((unsigned char)c) >> 4];
}
/**
* Moves pointers one byte forward.
*/
static void NextPos(const unsigned char** pos,
const char** key,
const char** multibyte_start)
{
++*pos;
if (*multibyte_start) {
/* Advance key to next byte in multibyte sequence. */
++*key;
/* Reset multibyte_start if last byte in multibyte sequence was consumed. */
if (*key - *multibyte_start == GetMultibyteLength(**multibyte_start))
*multibyte_start = 0;
} else {
if (GetMultibyteLength(**key)) {
/* Multibyte prefix was matched in the dafsa, start matching multibyte
* content in next round. */
*multibyte_start = *key;
} else {
/* Advance key as a single byte character was matched. */
++*key;
}
}
}
/*
* Read next offset from pos.
* Returns true if an offset could be read, false otherwise.
*/
static int GetNextOffset(const unsigned char** pos,
const unsigned char* end,
const unsigned char** offset)
{
size_t bytes_consumed;
if (*pos == end)
return 0;
/* When reading an offset the byte array must always contain at least
* three more bytes to consume. First the offset to read, then a node
* to skip over and finally a destination node. No object can be smaller
* than one byte. */
CHECK_LT(*pos + 2, end);
switch (**pos & 0x60) {
case 0x60: /* Read three byte offset */
*offset += (((*pos)[0] & 0x1F) << 16) | ((*pos)[1] << 8) | (*pos)[2];
bytes_consumed = 3;
break;
case 0x40: /* Read two byte offset */
*offset += (((*pos)[0] & 0x1F) << 8) | (*pos)[1];
bytes_consumed = 2;
break;
default:
*offset += (*pos)[0] & 0x3F;
bytes_consumed = 1;
}
if ((**pos & 0x80) != 0) {
*pos = end;
} else {
*pos += bytes_consumed;
}
return 1;
}
/*
* Check if byte at offset is last in label.
*/
static int IsEOL(const unsigned char* offset, const unsigned char* end)
{
CHECK_LT(offset, end);
return(*offset & 0x80) != 0;
}
/*
* Check if byte at offset matches first character in key.
* This version assumes a range check was already performed by the caller.
*/
static int IsMatchUnchecked(const unsigned char matcher,
const char* key,
const char* multibyte_start)
{
if (multibyte_start) {
/* Multibyte matching mode. */
if (multibyte_start == key) {
/* Match leading byte, which will also match the sequence length. */
return (matcher ^ 0x80) == (const unsigned char)*key;
} else {
/* Match following bytes. */
return (matcher ^ 0xC0) == (const unsigned char)*key;
}
}
/* If key points at a leading byte in a multibyte sequence, but we are not yet
* in multibyte mode, then the dafsa should contain a special byte to indicate
* a mode switch. */
if (GetMultibyteLength(*key)) {
return matcher == 0x1F;
}
/* Normal matching of a single byte character. */
return matcher == (const unsigned char)*key;
}
/*
* Check if byte at offset matches first character in key.
* This version matches characters not last in label.
*/
static int IsMatch(const unsigned char* offset,
const unsigned char* end,
const char* key,
const char* multibyte_start)
{
CHECK_LT(offset, end);
return IsMatchUnchecked(*offset, key, multibyte_start);
}
/*
* Check if byte at offset matches first character in key.
* This version matches characters last in label.
*/
static int IsEndCharMatch(const unsigned char* offset,
const unsigned char* end,
const char* key,
const char* multibyte_start)
{
CHECK_LT(offset, end);
return IsMatchUnchecked(*offset ^ 0x80, key, multibyte_start);
}
/*
* Read return value at offset.
* Returns true if a return value could be read, false otherwise.
*/
static int GetReturnValue(const unsigned char* offset,
const unsigned char* end,
const char* multibyte_start,
int* return_value)
{
CHECK_LT(offset, end);
if (!multibyte_start && (*offset & 0xE0) == 0x80) {
*return_value = *offset & 0x0F;
return 1;
}
return 0;
}
/*
* Looks up the string |key| with length |key_length| in a fixed set of
* strings. The set of strings must be known at compile time. It is converted to
* a graph structure named a DAFSA (Deterministic Acyclic Finite State
* Automaton) by the script psl-make-dafsa during compilation. This permits
* efficient (in time and space) lookup. The graph generated by psl-make-dafsa
* takes the form of a constant byte array which should be supplied via the
* |graph| and |length| parameters. The return value is kDafsaNotFound,
* kDafsaFound, or a bitmap consisting of one or more of kDafsaExceptionRule,
* kDafsaWildcardRule and kDafsaPrivateRule ORed together.
*
* Lookup a domain key in a byte array generated by psl-make-dafsa.
*/
/* prototype to skip warning with -Wmissing-prototypes */
int _HIDDEN LookupStringInFixedSet(const unsigned char*, size_t,const char*, size_t);
int _HIDDEN LookupStringInFixedSet(const unsigned char* graph,
size_t length,
const char* key,
size_t key_length)
{
const unsigned char* pos = graph;
const unsigned char* end = graph + length;
const unsigned char* offset = pos;
const char* key_end = key + key_length;
const char* multibyte_start = 0;
while (GetNextOffset(&pos, end, &offset)) {
/*char <char>+ end_char offsets
* char <char>+ return value
* char end_char offsets
* char return value
* end_char offsets
* return_value
*/
int did_consume = 0;
if (key != key_end && !IsEOL(offset, end)) {
/* Leading <char> is not a match. Don't dive into this child */
if (!IsMatch(offset, end, key, multibyte_start))
continue;
did_consume = 1;
NextPos(&offset, &key, &multibyte_start);
/* Possible matches at this point:
* <char>+ end_char offsets
* <char>+ return value
* end_char offsets
* return value
*/
/* Remove all remaining <char> nodes possible */
while (!IsEOL(offset, end) && key != key_end) {
if (!IsMatch(offset, end, key, multibyte_start))
return -1;
NextPos(&offset, &key, &multibyte_start);
}
}
/* Possible matches at this point:
* end_char offsets
* return_value
* If one or more <char> elements were consumed, a failure
* to match is terminal. Otherwise, try the next node.
*/
if (key == key_end) {
int return_value;
if (GetReturnValue(offset, end, multibyte_start, &return_value))
return return_value;
/* The DAFSA guarantees that if the first char is a match, all
* remaining char elements MUST match if the key is truly present.
*/
if (did_consume)
return -1;
continue;
}
if (!IsEndCharMatch(offset, end, key, multibyte_start)) {
if (did_consume)
return -1; /* Unexpected */
continue;
}
NextPos(&offset, &key, &multibyte_start);
pos = offset; /* Dive into child */
}
return -1; /* No match */
}
/* prototype to skip warning with -Wmissing-prototypes */
int _HIDDEN GetUtfMode(const unsigned char *graph, size_t length);
int _HIDDEN GetUtfMode(const unsigned char *graph, size_t length)
{
return length > 0 && graph[length - 1] < 0x80;
}