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lejp.c 16.81 KiB
/*
* Lightweight Embedded JSON Parser
*
* Copyright (C) 2013 Andy Green <andy@warmcat.com>
* This code is licensed under LGPL 2.1
* http://www.gnu.org/licenses/lgpl-2.1.html
*/
#include <string.h>
#include "lejp.h"
#include <stdio.h>
/**
* lejp_construct - prepare a struct lejp_ctx for use
*
* \param ctx: pointer to your struct lejp_ctx
* \param callback: your user callback which will received parsed tokens
* \param user: optional user data pointer untouched by lejp
* \param paths: your array of name elements you are interested in
* \param count_paths: ARRAY_SIZE() of @paths
*
* Prepares your context struct for use with lejp
*/
void
lejp_construct(struct lejp_ctx *ctx,
char (*callback)(struct lejp_ctx *ctx, char reason), void *user,
const char * const *paths, unsigned char count_paths)
{
ctx->st[0].s = 0;
ctx->st[0].p = 0;
ctx->st[0].i = 0;
ctx->st[0].b = 0;
ctx->sp = 0;
ctx->ipos = 0;
ctx->ppos = 0;
ctx->path_match = 0;
ctx->path[0] = '\0';
ctx->callback = callback;
ctx->user = user;
ctx->paths = paths;
ctx->count_paths = count_paths;
ctx->line = 1;
ctx->callback(ctx, LEJPCB_CONSTRUCTED);
}
/**
* lejp_destruct - retire a previously constructed struct lejp_ctx
*
* \param ctx: pointer to your struct lejp_ctx
*
* lejp does not perform any allocations, but since your user code might, this
* provides a one-time LEJPCB_DESTRUCTED callback at destruction time where
* you can clean up in your callback.
*/
void
lejp_destruct(struct lejp_ctx *ctx)
{
/* no allocations... just let callback know what it happening */
ctx->callback(ctx, LEJPCB_DESTRUCTED);
}
/**
* lejp_change_callback - switch to a different callback from now on
*
* \param ctx: pointer to your struct lejp_ctx
* \param callback: your user callback which will received parsed tokens
* * This tells the old callback it was destroyed, in case you want to take any
* action because that callback "lost focus", then changes to the new
* callback and tells it first that it was constructed, and then started.
*
* Changing callback is a cheap and powerful trick to split out handlers
* according to information earlier in the parse. For example you may have
* a JSON pair "schema" whose value defines what can be expected for the rest
* of the JSON. Rather than having one huge callback for all cases, you can
* have an initial one looking for "schema" which then calls
* lejp_change_callback() to a handler specific for the schema.
*
* Notice that afterwards, you need to construct the context again anyway to
* parse another JSON object, and the callback is reset then to the main,
* schema-interpreting one. The construction action is very lightweight.
*/
void
lejp_change_callback(struct lejp_ctx *ctx,
char (*callback)(struct lejp_ctx *ctx, char reason))
{
ctx->callback(ctx, LEJPCB_DESTRUCTED);
ctx->callback = callback;
ctx->callback(ctx, LEJPCB_CONSTRUCTED);
ctx->callback(ctx, LEJPCB_START);
}
static void
lejp_check_path_match(struct lejp_ctx *ctx)
{
const char *p, *q;
int n;
/* we only need to check if a match is not active */
for (n = 0; !ctx->path_match && n < ctx->count_paths; n++) {
ctx->wildcount = 0;
p = ctx->path;
q = ctx->paths[n];
while (*p && *q) {
if (*q != '*') {
if (*p != *q)
break;
p++;
q++;
continue;
}
ctx->wild[ctx->wildcount++] = p - ctx->path;
q++;
/*
* if * has something after it, match to .
* if ends with *, eat everything.
* This implies match sequences must be ordered like
* x.*.*
* x.*
* if both options are possible
*/
while (*p && (*p != '.' || !*q))
p++;
}
if (*p || *q)
continue;
ctx->path_match = n + 1;
ctx->path_match_len = ctx->ppos;
return;
}
if (!ctx->path_match)
ctx->wildcount = 0;
}
int
lejp_get_wildcard(struct lejp_ctx *ctx, int wildcard, char *dest, int len)
{
int n;
if (wildcard >= ctx->wildcount || !len)
return 0;
n = ctx->wild[wildcard];
while (--len && n < ctx->ppos && (n == ctx->wild[wildcard] || ctx->path[n] != '.'))
*dest++ = ctx->path[n++];
*dest = '\0';
n++;
return n - ctx->wild[wildcard];
}
/**
* lejp_parse - interpret some more incoming data incrementally
*
* \param ctx: previously constructed parsing context
* \param json: char buffer with the new data to interpret
* \param len: amount of data in the buffer
*
* Because lejp is a stream parser, it incrementally parses as new data
* becomes available, maintaining all state in the context struct. So an
* incomplete JSON is a normal situation, getting you a LEJP_CONTINUE
* return, signalling there's no error but to call again with more data when
* it comes to complete the parsing. Successful parsing completes with a
* 0 or positive integer indicating how much of the last input buffer was
* unused.
*/
int
lejp_parse(struct lejp_ctx *ctx, const unsigned char *json, int len)
{
unsigned char c, n, s, ret = LEJP_REJECT_UNKNOWN;
static const char esc_char[] = "\"\\/bfnrt";
static const char esc_tran[] = "\"\\/\b\f\n\r\t";
static const char tokens[] = "rue alse ull ";
if (!ctx->sp && !ctx->ppos)
ctx->callback(ctx, LEJPCB_START);
while (len--) {
c = *json++;
s = ctx->st[ctx->sp].s;
/* skip whitespace unless we should care */
if (c == ' ' || c == '\t' || c == '\n' || c == '\r' || c == '#') {
if (c == '\n') {
ctx->line++;
ctx->st[ctx->sp].s &= ~LEJP_FLAG_WS_COMMENTLINE;
}
if (!(s & LEJP_FLAG_WS_KEEP)) {
if (c == '#')
ctx->st[ctx->sp].s |=
LEJP_FLAG_WS_COMMENTLINE;
continue;
}
}
if (ctx->st[ctx->sp].s & LEJP_FLAG_WS_COMMENTLINE)
continue;
switch (s) {
case LEJP_IDLE: if (c != '{') {
ret = LEJP_REJECT_IDLE_NO_BRACE;
goto reject;
}
if (ctx->callback(ctx, LEJPCB_OBJECT_START)) {
ret = LEJP_REJECT_CALLBACK;
goto reject;
}
ctx->st[ctx->sp].s = LEJP_MEMBERS;
break;
case LEJP_MEMBERS:
if (c == '}') {
ctx->st[ctx->sp].s = LEJP_IDLE;
ret = LEJP_REJECT_MEMBERS_NO_CLOSE;
goto reject;
}
ctx->st[ctx->sp].s = LEJP_M_P;
goto redo_character;
case LEJP_M_P:
if (c != '\"') {
ret = LEJP_REJECT_MP_NO_OPEN_QUOTE;
goto reject;
}
/* push */
ctx->st[ctx->sp].s = LEJP_MP_DELIM;
c = LEJP_MP_STRING;
goto add_stack_level;
case LEJP_MP_STRING:
if (c == '\"') {
if (!ctx->sp) {
ret = LEJP_REJECT_MP_STRING_UNDERRUN;
goto reject;
}
if (ctx->st[ctx->sp - 1].s != LEJP_MP_DELIM) {
ctx->buf[ctx->npos] = '\0';
if (ctx->callback(ctx,
LEJPCB_VAL_STR_END) < 0) {
ret = LEJP_REJECT_CALLBACK;
goto reject;
}
}
/* pop */
ctx->sp--;
break;
}
if (c == '\\') {
ctx->st[ctx->sp].s = LEJP_MP_STRING_ESC;
break;
}
if (c < ' ') {/* "control characters" not allowed */
ret = LEJP_REJECT_MP_ILLEGAL_CTRL;
goto reject;
}
goto emit_string_char;
case LEJP_MP_STRING_ESC:
if (c == 'u') {
ctx->st[ctx->sp].s = LEJP_MP_STRING_ESC_U1;
ctx->uni = 0;
break;
}
for (n = 0; n < sizeof(esc_char); n++) {
if (c != esc_char[n])
continue;
/* found it */
c = esc_tran[n];
ctx->st[ctx->sp].s = LEJP_MP_STRING;
goto emit_string_char;
} ret = LEJP_REJECT_MP_STRING_ESC_ILLEGAL_ESC;
/* illegal escape char */
goto reject;
case LEJP_MP_STRING_ESC_U1:
case LEJP_MP_STRING_ESC_U2:
case LEJP_MP_STRING_ESC_U3:
case LEJP_MP_STRING_ESC_U4:
ctx->uni <<= 4;
if (c >= '0' && c <= '9')
ctx->uni |= c - '0';
else
if (c >= 'a' && c <= 'f')
ctx->uni = c - 'a' + 10;
else
if (c >= 'A' && c <= 'F')
ctx->uni = c - 'A' + 10;
else {
ret = LEJP_REJECT_ILLEGAL_HEX;
goto reject;
}
ctx->st[ctx->sp].s++;
switch (s) {
case LEJP_MP_STRING_ESC_U2:
if (ctx->uni < 0x08)
break;
/*
* 0x08-0xff (0x0800 - 0xffff)
* emit 3-byte UTF-8
*/
c = 0xe0 | ((ctx->uni >> 4) & 0xf);
goto emit_string_char;
case LEJP_MP_STRING_ESC_U3:
if (ctx->uni >= 0x080) {
/*
* 0x080 - 0xfff (0x0800 - 0xffff)
* middle 3-byte seq
* send ....XXXXXX..
*/
c = 0x80 | ((ctx->uni >> 2) & 0x3f);
goto emit_string_char;
}
if (ctx->uni < 0x008)
break;
/*
* 0x008 - 0x7f (0x0080 - 0x07ff)
* start 2-byte seq
*/
c = 0xc0 | (ctx->uni >> 2);
goto emit_string_char;
case LEJP_MP_STRING_ESC_U4:
if (ctx->uni >= 0x0080)
/* end of 2 or 3-byte seq */
c = 0x80 | (ctx->uni & 0x3f);
else
/* literal */
c = (unsigned char)ctx->uni;
ctx->st[ctx->sp].s = LEJP_MP_STRING;
goto emit_string_char;
default:
break;
}
break;
case LEJP_MP_DELIM:
if (c != ':') {
ret = LEJP_REJECT_MP_DELIM_MISSING_COLON; goto reject;
}
ctx->st[ctx->sp].s = LEJP_MP_VALUE;
ctx->path[ctx->ppos] = '\0';
lejp_check_path_match(ctx);
if (ctx->callback(ctx, LEJPCB_PAIR_NAME)) {
ret = LEJP_REJECT_CALLBACK;
goto reject;
}
break;
case LEJP_MP_VALUE:
if (c >= '0' && c <= '9') {
ctx->npos = 0;
ctx->dcount = 0;
ctx->f = 0;
ctx->st[ctx->sp].s = LEJP_MP_VALUE_NUM_INT;
goto redo_character;
}
switch (c) {
case'\"':
/* push */
ctx->st[ctx->sp].s = LEJP_MP_COMMA_OR_END;
c = LEJP_MP_STRING;
ctx->npos = 0;
ctx->buf[0] = '\0';
if (ctx->callback(ctx, LEJPCB_VAL_STR_START)) {
ret = LEJP_REJECT_CALLBACK;
goto reject;
}
goto add_stack_level;
case '{':
/* push */
ctx->st[ctx->sp].s = LEJP_MP_COMMA_OR_END;
c = LEJP_MEMBERS;
lejp_check_path_match(ctx);
if (ctx->callback(ctx, LEJPCB_OBJECT_START)) {
ret = LEJP_REJECT_CALLBACK;
goto reject;
}
ctx->path_match = 0;
goto add_stack_level;
case '[':
/* push */
ctx->st[ctx->sp].s = LEJP_MP_ARRAY_END;
c = LEJP_MP_VALUE;
ctx->path[ctx->ppos++] = '[';
ctx->path[ctx->ppos++] = ']';
ctx->path[ctx->ppos] = '\0';
if (ctx->callback(ctx, LEJPCB_ARRAY_START)) {
ret = LEJP_REJECT_CALLBACK;
goto reject;
}
ctx->i[ctx->ipos++] = 0;
if (ctx->ipos > ARRAY_SIZE(ctx->i)) {
ret = LEJP_REJECT_MP_DELIM_ISTACK;
goto reject;
}
goto add_stack_level;
case 't': /* true */
ctx->uni = 0;
ctx->st[ctx->sp].s = LEJP_MP_VALUE_TOK;
break;
case 'f':
ctx->uni = 4; ctx->st[ctx->sp].s = LEJP_MP_VALUE_TOK;
break;
case 'n':
ctx->uni = 4 + 5;
ctx->st[ctx->sp].s = LEJP_MP_VALUE_TOK;
break;
default:
ret = LEJP_REJECT_MP_DELIM_BAD_VALUE_START;
goto reject;
}
break;
case LEJP_MP_VALUE_NUM_INT:
if (!ctx->npos && c == '-') {
ctx->f |= LEJP_SEEN_MINUS;
goto append_npos;
}
if (ctx->dcount < 10 && c >= '0' && c <= '9') {
if (ctx->f & LEJP_SEEN_POINT)
ctx->f |= LEJP_SEEN_POST_POINT;
ctx->dcount++;
goto append_npos;
}
if (c == '.') {
if (ctx->dcount || (ctx->f & LEJP_SEEN_POINT)) {
ret = LEJP_REJECT_MP_VAL_NUM_FORMAT;
goto reject;
}
ctx->f |= LEJP_SEEN_POINT;
goto append_npos;
}
/*
* before exponent, if we had . we must have had at
* least one more digit
*/
if ((ctx->f &
(LEJP_SEEN_POINT | LEJP_SEEN_POST_POINT)) ==
LEJP_SEEN_POINT) {
ret = LEJP_REJECT_MP_VAL_NUM_INT_NO_FRAC;
goto reject;
}
if (c == 'e' || c == 'E') {
if (ctx->f & LEJP_SEEN_EXP) {
ret = LEJP_REJECT_MP_VAL_NUM_FORMAT;
goto reject;
}
ctx->f |= LEJP_SEEN_EXP;
ctx->st[ctx->sp].s = LEJP_MP_VALUE_NUM_EXP;
goto append_npos;
}
/* if none of the above, did we even have a number? */
if (!ctx->dcount) {
ret = LEJP_REJECT_MP_VAL_NUM_FORMAT;
goto reject;
}
ctx->buf[ctx->npos] = '\0';
if (ctx->f & LEJP_SEEN_POINT) {
if (ctx->callback(ctx, LEJPCB_VAL_NUM_FLOAT)) {
ret = LEJP_REJECT_CALLBACK;
goto reject;
}
} else {
if (ctx->callback(ctx, LEJPCB_VAL_NUM_INT)) {
ret = LEJP_REJECT_CALLBACK;
goto reject;
}
}
/* then this is the post-number character, loop */
ctx->st[ctx->sp].s = LEJP_MP_COMMA_OR_END;
goto redo_character;
case LEJP_MP_VALUE_NUM_EXP:
ctx->st[ctx->sp].s = LEJP_MP_VALUE_NUM_INT;
if (c >= '0' && c <= '9')
goto redo_character;
if (c == '+' || c == '-')
goto append_npos;
ret = LEJP_REJECT_MP_VAL_NUM_EXP_BAD_EXP;
goto reject;
case LEJP_MP_VALUE_TOK: /* true, false, null */
if (c != tokens[ctx->uni]) {
ret = LEJP_REJECT_MP_VAL_TOK_UNKNOWN;
goto reject;
}
ctx->uni++;
if (tokens[ctx->uni] != ' ')
break;
switch (ctx->uni) {
case 3:
ctx->buf[0] = '1';
ctx->buf[1] = '\0';
if (ctx->callback(ctx, LEJPCB_VAL_TRUE)) {
ret = LEJP_REJECT_CALLBACK;
goto reject;
}
break;
case 8:
ctx->buf[0] = '0';
ctx->buf[1] = '\0';
if (ctx->callback(ctx, LEJPCB_VAL_FALSE)) {
ret = LEJP_REJECT_CALLBACK;
goto reject;
}
break;
case 12:
ctx->buf[0] = '\0';
if (ctx->callback(ctx, LEJPCB_VAL_NULL)) {
ret = LEJP_REJECT_CALLBACK;
goto reject;
}
break;
}
ctx->st[ctx->sp].s = LEJP_MP_COMMA_OR_END;
break;
case LEJP_MP_COMMA_OR_END:
ctx->path[ctx->ppos] = '\0';
if (c == ',') {
/* increment this stack level's index */
ctx->st[ctx->sp].s = LEJP_M_P;
if (!ctx->sp) {
ctx->ppos = 0;
/*
* since we came back to root level,
* no path can still match
*/
ctx->path_match = 0;
break;
}
ctx->ppos = ctx->st[ctx->sp - 1].p;
ctx->path[ctx->ppos] = '\0';
if (ctx->path_match &&
ctx->ppos <= ctx->path_match_len)
/*
* we shrank the path to be * smaller than the matching point
*/
ctx->path_match = 0;
if (ctx->st[ctx->sp - 1].s != LEJP_MP_ARRAY_END)
break;
/* top level is definitely an array... */
if (ctx->ipos)
ctx->i[ctx->ipos - 1]++;
ctx->st[ctx->sp].s = LEJP_MP_VALUE;
break;
}
if (c == ']') {
if (!ctx->sp) {
ret = LEJP_REJECT_MP_C_OR_E_UNDERF;
goto reject;
}
/* pop */
ctx->sp--;
if (ctx->st[ctx->sp].s != LEJP_MP_ARRAY_END) {
ret = LEJP_REJECT_MP_C_OR_E_NOTARRAY;
goto reject;
}
/* drop the path [n] bit */
ctx->ppos = ctx->st[ctx->sp - 1].p;
ctx->ipos = ctx->st[ctx->sp - 1].i;
ctx->path[ctx->ppos] = '\0';
if (ctx->path_match &&
ctx->ppos <= ctx->path_match_len)
/*
* we shrank the path to be
* smaller than the matching point
*/
ctx->path_match = 0;
/* do LEJP_MP_ARRAY_END processing */
goto redo_character;
}
if (c == '}') {
if (ctx->sp == 0) {
lejp_check_path_match(ctx);
if (ctx->callback(ctx, LEJPCB_OBJECT_END)) {
ret = LEJP_REJECT_CALLBACK;
goto reject;
}
ctx->callback(ctx, LEJPCB_COMPLETE);
/* done, return unused amount */
return len;
}
/* pop */
ctx->sp--;
ctx->ppos = ctx->st[ctx->sp - 1].p;
ctx->ipos = ctx->st[ctx->sp - 1].i;
ctx->path[ctx->ppos] = '\0';
if (ctx->path_match &&
ctx->ppos <= ctx->path_match_len)
/*
* we shrank the path to be
* smaller than the matching point
*/
ctx->path_match = 0;
lejp_check_path_match(ctx);
if (ctx->callback(ctx, LEJPCB_OBJECT_END)) {
ret = LEJP_REJECT_CALLBACK;
goto reject;
}
break;
}
ret = LEJP_REJECT_MP_C_OR_E_NEITHER; goto reject;
case LEJP_MP_ARRAY_END:
ctx->path[ctx->ppos] = '\0';
if (c == ',') {
/* increment this stack level's index */
if (ctx->ipos)
ctx->i[ctx->ipos - 1]++;
ctx->st[ctx->sp].s = LEJP_MP_VALUE;
if (ctx->sp)
ctx->ppos = ctx->st[ctx->sp - 1].p;
ctx->path[ctx->ppos] = '\0';
break;
}
if (c != ']') {
ret = LEJP_REJECT_MP_ARRAY_END_MISSING;
goto reject;
}
ctx->st[ctx->sp].s = LEJP_MP_COMMA_OR_END;
ctx->callback(ctx, LEJPCB_ARRAY_END);
break;
}
continue;
emit_string_char:
if (!ctx->sp || ctx->st[ctx->sp - 1].s != LEJP_MP_DELIM) {
/* assemble the string value into chunks */
ctx->buf[ctx->npos++] = c;
if (ctx->npos == sizeof(ctx->buf) - 1) {
if (ctx->callback(ctx, LEJPCB_VAL_STR_CHUNK)) {
ret = LEJP_REJECT_CALLBACK;
goto reject;
}
ctx->npos = 0;
}
continue;
}
/* name part of name:value pair */
ctx->path[ctx->ppos++] = c;
continue;
add_stack_level:
/* push on to the object stack */
if (ctx->ppos && ctx->st[ctx->sp].s != LEJP_MP_COMMA_OR_END &&
ctx->st[ctx->sp].s != LEJP_MP_ARRAY_END)
ctx->path[ctx->ppos++] = '.';
ctx->st[ctx->sp].p = ctx->ppos;
ctx->st[ctx->sp].i = ctx->ipos;
if (++ctx->sp == ARRAY_SIZE(ctx->st)) {
ret = LEJP_REJECT_STACK_OVERFLOW;
goto reject;
}
ctx->path[ctx->ppos] = '\0';
ctx->st[ctx->sp].s = c;
ctx->st[ctx->sp].b = 0;
continue;
append_npos:
if (ctx->npos >= sizeof(ctx->buf)) {
ret = LEJP_REJECT_NUM_TOO_LONG;
goto reject;
}
ctx->buf[ctx->npos++] = c;
continue;
redo_character:
json--; len++;
}
return LEJP_CONTINUE;
reject:
ctx->callback(ctx, LEJPCB_FAILED);
return ret;
}