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scaner.c
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scaner.c
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#include <ctype.h> /* for isdigit */
#include <string.h> /* for memchr() */
#include <stdio.h>
#include <stdlib.h> /* for strtod() */
#include <stdarg.h>
#include <math.h> /* for the time being */
#include "util.h"
#include "scaner.h"
#include "scan_fp.h"
static const char* unrecog_token = "Unrecognizable token";
/* Forward decl */
static void __attribute__((format(printf, 3, 4), cold))
set_scan_err_fmt(scaner_t* scaner, const char* loc, const char* fmt, ...);
static void __attribute__((cold))
set_scan_err(scaner_t* scaner, const char* loc, const char* str);
static char token_predict[256];
static char esc_char[256];
#define TT_IS_SPACE (TT_LAST + 1)
static void
init_token_predict() {
memset(token_predict, TT_ERR, sizeof(token_predict));
/* Seperator */
{
int i, e;
const char* sep = "{}[],:";
for (i = 0, e = (int)strlen(sep); i < e; i++) {
uint8_t c = (uint8_t)sep[i];
token_predict[c] = TT_CHAR;
}
}
/* Null predictor */
token_predict['n'] = TT_NULL;
token_predict['N'] = TT_NULL;
/* Number(int/fp) predictor. NOTE: unlike C, numbers
* like +1.2 .5, -.4 are illegal.
*/
const char* np = "-0123456789";
int idx, idx_e;
for (idx = 0, idx_e = strlen(np); idx < idx_e; idx++) {
token_predict[(uint8_t)np[idx]] = TT_FP;
}
/* Boolean predictor */
const char* bp = "tTfF";
for (idx = 0, idx_e = strlen(bp); idx < idx_e; idx++) {
token_predict[(uint8_t)bp[idx]] = TT_BOOL;
}
/* string predictor */
token_predict['"'] = TT_STR;
token_predict[' '] = TT_IS_SPACE;
token_predict['\t'] = TT_IS_SPACE;
token_predict['\r'] = TT_IS_SPACE;
token_predict['\n'] = TT_IS_SPACE;
token_predict['\f'] = TT_IS_SPACE;
token_predict['\v'] = TT_IS_SPACE;
}
static void
init_esc_table() {
memset(esc_char, 0, sizeof(esc_char));
esc_char['"'] = '"';
esc_char['/'] = '/';
esc_char['\\'] = '\\';
esc_char['b'] = '\b';
esc_char['f'] = '\f';
esc_char['n'] = '\n';
esc_char['r'] = '\r';
esc_char['t'] = '\t';
}
static void __attribute__((constructor))
init_const_table() {
init_token_predict();
init_esc_table();
}
/* On success, scaner advance the pointer right after the token just
* recognized, and the token_t::span records span of the token in
* input string.
*/
static inline void
update_ptr_on_succ(scaner_t* scaner, const char* scan_starts,
int32_t span) {
scaner->scan_ptr = scan_starts + span;
scaner->token.span = span;
scaner->col_num += span;
}
/* On failure, scaner's pointer is not advanced, and token_t::span points
* to the locations where lexical error takes place.
*/
static inline void
update_ptr_on_failure(scaner_t* scaner, const char* scan_starts,
int32_t span) {
scaner->scan_ptr = scan_starts;
scaner->token.span = span;
scaner->token.type = TT_ERR;
}
static token_t*
char_handler(scaner_t* scaner, const char* str, const char* str_e) {
update_ptr_on_succ(scaner, str, 1);
token_t* tk = &scaner->token;
tk->type = TT_CHAR;
tk->char_val = *str;
return tk;
}
static token_t*
null_handler(scaner_t* scaner, const char* str, const char* str_e) {
token_t* tk = &scaner->token;
if (str + 4 < str_e && !strncmp(str, "null", 4)) {
update_ptr_on_succ(scaner, str, 4);
tk->type = TT_NULL;
return tk;
}
update_ptr_on_failure(scaner, str, 0);
if (str + 4 < str_e && !strncasecmp(str, "null", 4)) {
set_scan_err(scaner, str, "'null' must be in lower case");
} else {
set_scan_err(scaner, str, 0);
}
return tk;
}
static token_t*
fp_handler(scaner_t* scaner, const char* str, const char* str_e) {
const char* advance = str;
int_db_union_t val;
int res = scan_fp(&advance, str_e, &val);
token_t* tk = &scaner->token;
if (res == 1) {
update_ptr_on_succ(scaner, str, advance - str);
tk->type = TT_INT64,
tk->int_val = val.int_val;
} else if (res == 2) {
update_ptr_on_succ(scaner, str, advance - str);
tk->type = TT_FP,
tk->db_val = val.db_val;
} else {
update_ptr_on_failure(scaner, str, advance - str);
}
return tk;
}
static token_t*
bool_handler(scaner_t* scaner, const char* str, const char* str_e) {
int len = str_e - str;
token_t* tk = &scaner->token;
tk->type = TT_BOOL;
if (len >= 5) {
if (!strncmp(str, "true", 4)) {
tk->int_val = 1;
update_ptr_on_succ(scaner, str, 4);
return tk;
}
if (!strncmp(str, "false", 5)) {
tk->int_val = 0;
update_ptr_on_succ(scaner, str, 5);
return tk;
}
}
update_ptr_on_failure(scaner, str, 0);
/* Emit eror-message if true/false is not in lower case, or the token
* starts with [tTfF], but is not boolean value at all.
*/
if ((len >= 4 && strncasecmp(str, "true", 4)) ||
(len >= 5 && strncasecmp(str, "false", 5))) {
set_scan_err(scaner, str, "boolean value must be in lower case");
} else {
set_scan_err(scaner, str, 0);
}
return tk;
}
static token_t*
unknown_tk_handler(scaner_t* scaner, const char* str, const char* str_e) {
token_t* tk = &scaner->token;
update_ptr_on_failure(scaner, str, 0);
set_scan_err(scaner, str, 0);
return tk;
}
/* ***********************************************************************
*
* Handle String
*
* ***********************************************************************
*/
/* The input "hex4" is a string with *four* leading hex-digits,
* this function is to convert them into an positive integer.
*
* For instance, given input hex4 being "aBc9...", the return value would
* be 0xabc9. Hexadecimal digits are case insensitive. If the leading
* four character include non-hex-digit, -1 is returned.
*
* NOTE: It's up to the caller to ensure the length of "hex4" is no less
* than 4.
*/
static int32_t
hex4_to_int(const char* hex4) {
unsigned char c = *hex4++;
int hval = 0, value;
if (c >= '0' && c <= '9')
hval = c - '0';
else if ((c | 0x20) >= 'a' && (c | 0x20) <= 'f') {
hval = (c | 0x20) - 'a' + 10;
} else {
return -1;
}
value = hval;
c = *hex4++;
if (c >= '0' && c <= '9')
hval = c - '0';
else if ((c | 0x20) >= 'a' && (c | 0x20) <= 'f') {
hval = (c | 0x20) - 'a' + 10;
} else {
return -1;
}
value = (value << 4) | hval;
c = *hex4++;
if (c >= '0' && c <= '9')
hval = c - '0';
else if ((c | 0x20) >= 'a' && (c | 0x20) <= 'f') {
hval = (c | 0x20) - 'a' + 10;
} else {
return -1;
}
value = (value << 4) | hval;
c = *hex4++;
if (c >= '0' && c <= '9')
hval = c - '0';
else if ((c | 0x20) >= 'a' && (c | 0x20) <= 'f') {
hval = (c | 0x20) - 'a' + 10;
} else {
return -1;
}
value = (value << 4) | hval;
return value;
}
/* determine the number of bytes needed to encode the given codepoint */
static int
utf8_encode_len(int codepoint) {
if (codepoint < 0x80)
return 1;
if (codepoint < 0x800)
return 2;
if (codepoint < 0x10000)
return 3;
return 4;
}
/* Encode the given codepoint in a sequence of UTF-8s */
static void
utf8_encode(char* buf, int codepoint, int len) {
static unsigned char len_mark[] = {0, 0xc0, 0xe0, 0xf0 };
switch (len) {
case 4: *(buf + 3) = ((codepoint | 0x80) & 0xbf);
codepoint >>= 6;
/* fall through */
case 3: *(buf + 2) = ((codepoint | 0x80) & 0xbf);
codepoint >>= 6;
/* fall through */
case 2: *(buf + 1) = ((codepoint | 0x80) & 0xbf);
codepoint >>= 6;
/* fall through */
default: break;
}
*buf = codepoint | len_mark[len - 1];
}
/* Process \u escape.
*
* The legal input string falls in one of the following two cases:
* 1. "\uzzzz", where the zzzz in (0, 0xD800] (Note zzzz > 0)
* 2. "\uxxxx\uyyyy", where the xxxx in [0xD800, 0xDBFF] yyyy in [DC00,DFFF].
* i.e. the input string is a UTF-16 surrogate pair.
*
* This function is to convert the input string to up to four UTF-8s and
* save them to "dest".
*
* On success, return 1, and the "src_advance" and "dest_advance" is set to
* the amount of byte the source and the destination string need to advance,
* respectively. Otherwise, 0 is returned.
*/
static const char* illegal_u_esc = "Illegal \\u escape";
static int
process_u_esc(scaner_t* scaner, const char* src, const char* src_end,
char* dest, int* src_advance, int* dest_advance) {
int32_t codepoint;
/* Step 1: get the codepoint */
if (unlikely(src + 6 > src_end))
return 0;
codepoint = hex4_to_int(src + 2);
if (unlikely(codepoint < 0)) {
set_scan_err(scaner, src, illegal_u_esc);
return 0;
}
*src_advance = 6; /* skip the \\uxxxx, hence 6 */
/* Detect UTF-16 surrogate pair. The codepoint be in this form : 110110x...
*/
if (codepoint >= 0xd800) {
int32_t codepoint_low;
const char* lower = src + 6;
if (codepoint & 0x400) {
set_scan_err(scaner, src, "Higher part of UTF-16 surrogate must "
"be in the range of [0xd800, 0xdbff]");
return 0;
}
if (unlikely(src + 12 > src_end) ||
unlikely(*(src + 6) != '\\') || unlikely(*(src + 7) != 'u')) {
set_scan_err(scaner, src + 6,
"Expect \\u escape for lower part "
"of UTF-16 surrogate");
return 0;
}
codepoint_low = hex4_to_int(lower + 2);
if (codepoint_low < 0) {
set_scan_err(scaner, lower, illegal_u_esc);
return 0;
}
if (unlikely(codepoint_low < 0xdc00) ||
unlikely(codepoint_low > 0xdfff)) {
set_scan_err(scaner, lower, "Lower part of UTF-16 surrogate must "
"be in the range of [0xdc00, 0xdfff]");
return 0;
}
/* Extract the lower 10-bit from surrogate pairs, and concatenate
* them together.
*/
codepoint = (codepoint_low & 0x3ff) | ((codepoint & 0x3ff) << 10);
codepoint |= 0x10000;
*src_advance = 12; /* skip the "\\uxxxx\\uyyyy", hence 12 */
}
/* Step 2: Encode the codepoint with UTF-8 sequence */
utf8_encode(dest, codepoint, *dest_advance = utf8_encode_len(codepoint));
return 1;
}
static token_t*
str_handler(scaner_t* scaner, const char* str, const char* str_e) {
/* step 1: determine the end of string */
const char* str_quote = str;
token_t* tk = &scaner->token;
do {
str_quote = memchr(str_quote + 1, '"', str_e - str_quote);
if (unlikely(!str_quote)) {
/* The string dose not end with quote*/
set_scan_err(scaner, str, "String does not end with quote");
return tk;
}
if (likely(*(str_quote - 1) != '\\')) {
break;
} else {
/* Consider the cases like "Junk\\" */
const char* t = str_quote - 2;
int cnt = 1;
for (; *t == '\\'; t--, cnt++) {}
if ((cnt & 1) == 0) {
break;
}
}
} while(1);
/* step 2: allocate space for the string. The new string has trailing
* '\0' for easing purpose.
*/
char* new_str =
MEMPOOL_ALLOC_TYPE_N(scaner->mempool, char, str_quote - str);
if (unlikely(!new_str)) {
set_scan_err(scaner, str, "OOM");
return tk;
}
/* step 3: copy the string */
{
char* dest = new_str;
const char* src = str + 1;
do {
int len = str_quote - src;
char* esc = (char*)memchr(src, '\\', len);
if (!esc) {
memcpy(dest, src, len);
src += len;
dest += len;
*dest = '\0'; /* to ease debugging*/
tk->str_val = new_str;
tk->str_len = dest - new_str;
tk->type = TT_STR;
update_ptr_on_succ(scaner, str, str_quote - str + 1);
return tk;
}
/* Handle escape */
len = esc - src;
memcpy(dest, src, len);
src = esc;
dest += len;
char esc_key = esc[1];
char esc_val = esc_char[(unsigned char)esc_key];
/* successfully processed non-unicode (\u) escape */
if (esc_val) {
*dest++ = esc_val;
src += sizeof("\\n") - 1;
continue;
}
/* process unicode escape */
if (esc_key == 'u') {
int src_adv, dest_adv;
if (process_u_esc(scaner, src, str_quote, dest,
&src_adv, &dest_adv)) {
src += src_adv;
dest += dest_adv;
continue;
}
}
/* illegal escape */
set_scan_err_fmt(scaner, esc, "illegal escape \\%c", esc[1]);
return tk;
} while(1);
}
/* Should not reach here. The return-statement is just to make
* stupid compilers happy.
*/
ASSERT(0);
return NULL;
}
static token_t* space_handler(scaner_t*, const char*, const char*);
typedef token_t* (*tk_hd_func)(scaner_t*, const char*, const char*);
tk_hd_func token_handler[] = {
[TT_INT64] = 0,
[TT_FP] = fp_handler,
[TT_STR] = str_handler,
[TT_BOOL] = bool_handler,
[TT_NULL] = null_handler,
[TT_CHAR] = char_handler,
[TT_ERR] = unknown_tk_handler,
[TT_IS_SPACE] = space_handler,
};
static token_t*
space_handler(scaner_t* scaner, const char* str_ptr, const char* str_end) {
int32_t ln = 0;
int32_t col = 0;
char lookahead = *str_ptr;
token_ty_t tt;
do {
col = (lookahead == '\n') ? 1 : col + 1;
ln += ((lookahead == '\n') ? 1 : 0);
if (unlikely(str_end <= ++str_ptr)) {
scaner->token.type = TT_END;
return &scaner->token;
}
lookahead = *str_ptr;
tt = (token_ty_t)token_predict[(uint32_t)(uint8_t)lookahead];
if (tt != TT_IS_SPACE)
break;
} while (1);
scaner->line_num += ln;
scaner->col_num += col;
/* It is not necessary to set scan_ptr as token-handler will update it.*/
/*scaner->scan_ptr = str_ptr; */
return token_handler[tt](scaner, str_ptr, str_end);
}
token_t*
sc_get_token(scaner_t* scaner, const char* str_end) {
const char* str_ptr = scaner->scan_ptr;
ASSERT(str_end == scaner->json_end);
if (unlikely(str_ptr >= str_end)) {
scaner->token.type = TT_END;
return &scaner->token;
}
char lookahead = *str_ptr;
token_ty_t tt = (token_ty_t)token_predict[(uint32_t)(uint8_t)lookahead];
return token_handler[tt](scaner, str_ptr, str_end);
}
void
sc_init_scaner(scaner_t* scaner, mempool_t* mp,
const char* json, uint32_t json_len) {
scaner->mempool = mp;
scaner->json_begin = json;
scaner->json_end = json + json_len;
scaner->scan_ptr = json;
scaner->line_num = 1;
scaner->col_num = 1;
scaner->err_msg = NULL;
}
void
sc_rewind (scaner_t* scaner) {
int span = scaner->token.span;
scaner->scan_ptr -= span;
scaner->col_num -= span;
}
/****************************************************************
*
* Error handling and other cold code cluster here
*
*****************************************************************
*/
static void __attribute__((format(printf, 3, 4)))
set_scan_err_fmt(scaner_t* scaner, const char* loc, const char* fmt, ...) {
if (scaner->err_msg)
return;
token_t* tk = &scaner->token;
tk->type = TT_ERR;
int buf_len = 250;
char* buf = MEMPOOL_ALLOC_TYPE_N(scaner->mempool, char, buf_len);
if (!buf) {
scaner->err_msg = "OOM";
return;
}
scaner->err_msg = buf;
int span = loc - scaner->scan_ptr;
int loc_info_len = snprintf(buf, buf_len, "(line:%d,col:%d) ",
scaner->line_num, scaner->col_num + span);
buf += loc_info_len;
buf_len -= loc_info_len;
va_list vl;
va_start(vl, fmt);
vsnprintf(buf, buf_len, fmt, vl);
va_end(vl);
}
static void __attribute__((cold))
set_scan_err(scaner_t* scaner, const char* loc, const char* str) {
if (scaner->err_msg)
return;
if (!str) { str = unrecog_token; }
set_scan_err_fmt(scaner, loc, "%s", str);
}