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/*
* Copyright (c) 2026, Apollo Telephone Laboratories.
* Provided under the BSD-3 clause.
*/
#include <ctype.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#include "defconf/lexer.h"
#include "defconf/ptrbox.h"
#include "defconf/trace.h"
/* Constants */
#define MAX_KW_LEN 32
#define MAX_NUM_LEN 20
/*
* Returns true if the given character is a whitespace character
*
* @c: Character to check
*/
static inline bool
lexer_is_ws(char c)
{
switch (c) {
case '\t':
case ' ':
case '\f':
case '\r':
case '\n':
return true;
}
return false;
}
/*
* Place a character back in the putback buffer
*
* @state: Defconf state
* @c: Character to put back
*/
static inline void
lexer_putback(struct defconf_state *state, int c)
{
if (state == NULL) {
return;
}
state->lex_cache = c;
}
/*
* Nom a single character from the input source file
*
* @state: Defconf state machine
* @skip_ws: If true, skip whitespace
*
* Returns the character on success, otherwise EOF on failure
*/
static int
lexer_nom(struct defconf_state *state, bool skip_ws)
{
int c;
if (state == NULL) {
return EOF;
}
if ((c = state->lex_cache) != '\0') {
state->lex_cache = '\0';
if (lexer_is_ws(c) && !skip_ws)
return c;
if (!lexer_is_ws(c))
return c;
}
while ((c = fgetc(state->in_fp)) != EOF) {
if (lexer_is_ws(c) && skip_ws)
continue;
break;
}
return c;
}
/*
* Scan a keyword
*
* @state: Defconf state
* @lc: Last character provided
*/
static char *
lexer_scan_ident(struct defconf_state *state, int lc)
{
char c, buf[MAX_KW_LEN];
size_t bufind = 0;
if (state == NULL) {
return NULL;
}
if (!isalpha(lc)) {
return NULL;
}
buf[bufind++] = lc;
for (;;) {
if (bufind >= sizeof(buf) - 1) {
trace_fatal(state, "token exceeds maximum length\n");
return NULL;
}
c = lexer_nom(state, false);
if (!isalnum(c) && c != '_') {
lexer_putback(state, c);
buf[bufind] = '\0';
return ptrbox_strdup(&state->ptrbox, buf);
}
buf[bufind++] = c;
}
return NULL;
}
/*
* Scan a number
*
* @state: Defconf state
* @lc: Last character provided
* @result: Result is written here
*/
static int
lexer_scan_num(struct defconf_state *state, int lc, struct token *result)
{
char c, buf[MAX_NUM_LEN + 1];
size_t bufind = 0;
if (state == NULL || result == NULL) {
return -1;
}
if (!isdigit(lc)) {
return -1;
}
buf[bufind++] = lc;
for (;;) {
if (bufind >= sizeof(buf) - 1) {
trace_fatal(state, "digits exceed maximum length\n");
return -1;
}
c = lexer_nom(state, false);
if (!isdigit(c)) {
lexer_putback(state, c);
buf[bufind] = '\0';
/* Set the token */
result->type = TT_INTLIT;
result->v = atoi(buf);
return 0;
}
buf[bufind++] = c;
}
return -1;
}
/*
* Check if a keyword matches against known keywords
*
* @kw: Keyword to check
* @result: Result is written here
*
* Returns zero on success
*/
static int
lexer_check_kw(const char *kw, struct token *result)
{
if (kw == NULL || result == NULL) {
return -1;
}
switch (*kw) {
case 'd':
if (strcmp(kw, "define") == 0) {
result->type = TT_DEFINE;
return 0;
}
break;
case 't':
if (strcmp(kw, "true") == 0) {
result->type = TT_TRUE;
return 0;
}
break;
case 'f':
if (strcmp(kw, "false") == 0) {
result->type = TT_FALSE;
return 0;
}
break;
}
return -1;
}
int
lexer_scan(struct defconf_state *state, struct token *result)
{
int c;
char *ident;
int error;
if (state == NULL || result == NULL) {
return -1;
}
if ((c = lexer_nom(state, true)) == EOF) {
return -1;
}
/* Scan for an identifier */
if ((ident = lexer_scan_ident(state, c)) != NULL) {
if (lexer_check_kw(ident, result) == 0) {
return 0;
}
result->type = TT_IDENT;
result->s = ident;
return 0;
}
/* Is this a digit? */
if (isdigit(c)) {
error = lexer_scan_num(state, c, result);
if (error < 0) {
return -1;
}
return 0;
}
trace_fatal(state, "unexpected token '%c'\n", c);
return -1;
}
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