native_dynamic_request_fields.c

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/**
 * @file
 * @brief URL decoding, query-string parsing, and form-value extraction
 *        for in-process dynamic request handling.
 */
 
#include "native_dynamic_request_fields.h"
 
#include <ctype.h>
#include <stdlib.h>
#include <string.h>
 
/* ------------------------------------------------------------------ */
/* URL decoding                                                        */
/* ------------------------------------------------------------------ */
 
static int hex_digit_value(char c) {
  if (c >= '0' && c <= '9') return c - '0';
  if (c >= 'A' && c <= 'F') return 10 + (c - 'A');
  if (c >= 'a' && c <= 'f') return 10 + (c - 'a');
  return -1;
}
 
char *native_dynamic_url_decode(const char *encoded) {
  size_t len;
  char *out;
  size_t i;
  size_t j;
 
  if (encoded == NULL) {
    return NULL;
  }
 
  len = strlen(encoded);
  out = (char *)malloc(len + 1);
  if (out == NULL) {
    return NULL;
  }
 
  i = 0;
  j = 0;
  while (i < len) {
    if (encoded[i] == '+' ) {
      out[j++] = ' ';
      i++;
    } else if (encoded[i] == '%' && (i + 2) < len) {
      int hi = hex_digit_value(encoded[i + 1]);
      int lo = hex_digit_value(encoded[i + 2]);
      if (hi >= 0 && lo >= 0) {
        out[j++] = (char)((hi << 4) | lo);
        i += 3;
      } else {
        out[j++] = encoded[i++];
      }
    } else {
      out[j++] = encoded[i++];
    }
  }
  out[j] = '\0';
  return out;
}
 
/* ------------------------------------------------------------------ */
/* Internal: extract a value from a key=value pair string              */
/* ------------------------------------------------------------------ */
 
static char *extract_value_for_key(const char *source, const char *key, char separator) {
  const char *cursor;
  size_t key_len;
 
  if (source == NULL || key == NULL || key[0] == '\0') {
    return NULL;
  }
 
  key_len = strlen(key);
  cursor = source;
 
  while (*cursor != '\0') {
    /* skip leading separator */
    if (cursor != source && *(cursor - 1) != separator) {
      /* not at the start of a pair; advance until we find a separator */
      while (*cursor != '\0' && *cursor != separator) {
        cursor++;
      }
      if (*cursor == '\0') {
        break;
      }
    }
 
    /* skip the separator itself */
    if (*cursor == separator) {
      cursor++;
    }
 
    /* trim inter-pair whitespace such as "; " in Cookie headers */
    while (*cursor == ' ' || *cursor == '\t') {
      cursor++;
    }
 
    /* check if the key matches */
    if (strncmp(cursor, key, key_len) == 0 && cursor[key_len] == '=') {
      const char *value_start = cursor + key_len + 1;
      const char *value_end;
      size_t value_len;
      char *decoded;
 
      /* find the end of this pair */
      value_end = value_start;
      while (*value_end != '\0' && *value_end != separator) {
        value_end++;
      }
 
      value_len = (size_t)(value_end - value_start);
      {
        char *raw = (char *)malloc(value_len + 1);
        if (raw == NULL) {
          return NULL;
        }
        memcpy(raw, value_start, value_len);
        raw[value_len] = '\0';
        decoded = native_dynamic_url_decode(raw);
        free(raw);
        return decoded;
      }
    }
 
    /* advance past this pair */
    while (*cursor != '\0' && *cursor != separator) {
      cursor++;
    }
  }
 
  return NULL;
}
 
/* ------------------------------------------------------------------ */
/* Public API                                                          */
/* ------------------------------------------------------------------ */
 
char *native_dynamic_query_value(const char *query, const char *key) {
  return extract_value_for_key(query, key, '&');
}
 
char *native_dynamic_form_value(const char *body, const char *key) {
  return extract_value_for_key(body, key, '&');
}
 
char *native_dynamic_cookie_value(const char *cookie_header, const char *name) {
  return extract_value_for_key(cookie_header, name, ';');
}