multipart_parser.c

/* Based on node-formidable by Felix Geisendörfer 
 * Igor Afonov - afonov@gmail.com - 2012
 * MIT License - http://www.opensource.org/licenses/mit-license.php
 */

#include "multipart_parser.h"

#include <stdio.h>
#include <stdarg.h>
#include <string.h>

static void multipart_log(const char * format, ...)
{
#ifdef DEBUG_MULTIPART
    va_list args;
    va_start(args, format);

    fprintf(stderr, "[HTTP_MULTIPART_PARSER] %s:%d: ", __FILE__, __LINE__);
    vfprintf(stderr, format, args);
    fprintf(stderr, "\n");
#endif
}

#define NOTIFY_CB(FOR)                                                 \
do {                                                                   \
  if (p->settings->on_##FOR) {                                         \
    if (p->settings->on_##FOR(p) != 0) {                               \
      return i;                                                        \
    }                                                                  \
  }                                                                    \
} while (0)

#define EMIT_DATA_CB(FOR, ptr, len)                                    \
do {                                                                   \
  if (p->settings->on_##FOR) {                                         \
    if (p->settings->on_##FOR(p, ptr, len) != 0) {                     \
      return i;                                                        \
    }                                                                  \
  }                                                                    \
} while (0)


#define LF 10
#define CR 13

struct multipart_parser {
  void * data;

  size_t index;
  size_t boundary_length;

  unsigned char state;

  const multipart_parser_settings* settings;

  char* lookbehind;
  char multipart_boundary[1];
};

enum state {
  s_uninitialized = 1,
  s_start,
  s_start_boundary,
  s_header_field_start,
  s_header_field,
  s_headers_almost_done,
  s_header_value_start,
  s_header_value,
  s_header_value_almost_done,
  s_part_data_start,
  s_part_data,
  s_part_data_almost_boundary,
  s_part_data_boundary,
  s_part_data_almost_end,
  s_part_data_end,
  s_part_data_final_hyphen,
  s_end
};

multipart_parser* multipart_parser_init
    (const char *boundary, const multipart_parser_settings* settings) {

  multipart_parser* p = malloc(sizeof(multipart_parser) +
                               strlen(boundary) +
                               strlen(boundary) + 9);

  strcpy(p->multipart_boundary, boundary);
  p->boundary_length = strlen(boundary);
  
  p->lookbehind = (p->multipart_boundary + p->boundary_length + 1);

  p->index = 0;
  p->state = s_start;
  p->settings = settings;

  return p;
}

void multipart_parser_free(multipart_parser* p) {
  free(p);
}

void multipart_parser_set_data(multipart_parser *p, void *data) {
    p->data = data;
}

void *multipart_parser_get_data(multipart_parser *p) {
    return p->data;
}

size_t multipart_parser_execute(multipart_parser* p, const char *buf, size_t len) {
  size_t i = 0;
  size_t mark = 0;
  char c, cl;
  int is_last = 0;

  while(i < len) {
    c = buf[i];
    is_last = (i == (len - 1));
    switch (p->state) {
      case s_start:
        multipart_log("s_start");
        p->index = 0;
        p->state = s_start_boundary;

      /* fallthrough */
      case s_start_boundary:
        multipart_log("s_start_boundary");
        if (p->index == p->boundary_length) {
          if (c != CR) {
            return i;
          }
          p->index++;
          break;
        } else if (p->index == (p->boundary_length + 1)) {
          if (c != LF) {
            return i;
          }
          p->index = 0;
          NOTIFY_CB(part_data_begin);
          p->state = s_header_field_start;
          break;
        }
        if (c != p->multipart_boundary[p->index]) {
          return i;
        }
        p->index++;
        break;

      case s_header_field_start:
        multipart_log("s_header_field_start");
        mark = i;
        p->state = s_header_field;

      /* fallthrough */
      case s_header_field:
        multipart_log("s_header_field");
        if (c == CR) {
          p->state = s_headers_almost_done;
          break;
        }

        if (c == ':') {
          EMIT_DATA_CB(header_field, buf + mark, i - mark);
          p->state = s_header_value_start;
          break;
        }

        cl = tolower(c);
        if ((c != '-') && (cl < 'a' || cl > 'z')) {
          multipart_log("invalid character in header name");
          return i;
        }
        if (is_last)
            EMIT_DATA_CB(header_field, buf + mark, (i - mark) + 1);
        break;

      case s_headers_almost_done:
        multipart_log("s_headers_almost_done");
        if (c != LF) {
          return i;
        }

        p->state = s_part_data_start;
        break;

      case s_header_value_start:
        multipart_log("s_header_value_start");
        if (c == ' ') {
          break;
        }

        mark = i;
        p->state = s_header_value;

      /* fallthrough */
      case s_header_value:
        multipart_log("s_header_value");
        if (c == CR) {
          EMIT_DATA_CB(header_value, buf + mark, i - mark);
          p->state = s_header_value_almost_done;
          break;
        }
        if (is_last)
            EMIT_DATA_CB(header_value, buf + mark, (i - mark) + 1);
        break;

      case s_header_value_almost_done:
        multipart_log("s_header_value_almost_done");
        if (c != LF) {
          return i;
        }
        p->state = s_header_field_start;
        break;

      case s_part_data_start:
        multipart_log("s_part_data_start");
        NOTIFY_CB(headers_complete);
        mark = i;
        p->state = s_part_data;

      /* fallthrough */
      case s_part_data:
        multipart_log("s_part_data");
        if (c == CR) {
            EMIT_DATA_CB(part_data, buf + mark, i - mark);
            mark = i;
            p->state = s_part_data_almost_boundary;
            p->lookbehind[0] = CR;
            break;
        }
        if (is_last)
            EMIT_DATA_CB(part_data, buf + mark, (i - mark) + 1);
        break;

      case s_part_data_almost_boundary:
        multipart_log("s_part_data_almost_boundary");
        if (c == LF) {
            p->state = s_part_data_boundary;
            p->lookbehind[1] = LF;
            p->index = 0;
            break;
        }
        EMIT_DATA_CB(part_data, p->lookbehind, 1);
        p->state = s_part_data;
        mark = i --;
        break;

      case s_part_data_boundary:
        multipart_log("s_part_data_boundary");
        if (p->multipart_boundary[p->index] != c) {
          EMIT_DATA_CB(part_data, p->lookbehind, 2 + p->index);
          p->state = s_part_data;
          mark = i --;
          break;
        }
        p->lookbehind[2 + p->index] = c;
        if ((++ p->index) == p->boundary_length) {
            NOTIFY_CB(part_data_end);
            p->state = s_part_data_almost_end;
        }
        break;

      case s_part_data_almost_end:
        multipart_log("s_part_data_almost_end");
        if (c == '-') {
            p->state = s_part_data_final_hyphen;
            break;
        }
        if (c == CR) {
            p->state = s_part_data_end;
            break;
        }
        return i;
   
      case s_part_data_final_hyphen:
        multipart_log("s_part_data_final_hyphen");
        if (c == '-') {
            NOTIFY_CB(body_end);
            p->state = s_end;
            break;
        }
        return i;

      case s_part_data_end:
        multipart_log("s_part_data_end");
        if (c == LF) {
            p->state = s_header_field_start;
            NOTIFY_CB(part_data_begin);
            break;
        }
        return i;

      case s_end:
        multipart_log("s_end: %02X", (int) c);
        break;

      default:
        multipart_log("Multipart parser unrecoverable error");
        return 0;
    }
    ++ i;
  }

  return len;
}