gistfile1.h

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <netdb.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <fcntl.h>
#include <string.h>
#include <sys/wait.h>
#include <signal.h>
#include <pthread.h>
#include <gc/gc.h>

int tcp_bind(unsigned int port){
  struct sockaddr_in inet_addr;
  int fd;

  inet_addr.sin_family=AF_INET;
  inet_addr.sin_port=htons(port);
  inet_addr.sin_addr.s_addr = INADDR_ANY;

  fd = socket(PF_INET, SOCK_STREAM, 0);
  if (fd == -1){
    perror("socket");
    exit(EXIT_FAILURE);
  }
  
  if (bind(fd,(struct sockaddr*)&inet_addr,
           sizeof(inet_addr))==-1){
    close(fd);
    perror("bind");
    exit(EXIT_FAILURE);
  }
  
  if (listen(fd, 3) == -1){
    perror("bind");
    exit(EXIT_FAILURE);
  }

  return fd;
}

static size_t scgi_read_length(FILE* stream){
  size_t res = 0;
  int ch;
  while ((ch = fgetc(stream)) != EOF){
    if (ch == ':'){
      return res;
    } else if (ch >= '0' && ch <= '9'){
      res *= 10;
      res += ch - '0';
    } else {
      abort(); // error
    }
  }
}

typedef struct buffer_t {
  char* ptr;
  size_t len;
} buffer_t;

buffer_t* scgi_read_netstring(FILE* stream){
  size_t res;
  buffer_t* bs = GC_NEW(buffer_t);
  bs->len = scgi_read_length(stream);
  bs->ptr = GC_MALLOC_ATOMIC(bs->len);
  res  = fread(bs->ptr, 1, bs->len, stream);
  if (res != bs->len){
    abort(); // error
  }
  if (fgetc(stream) != ','){
    abort(); // error
  }
  return bs;
}

void scgi_read_headers(FILE* stream){
  buffer_t* buf = scgi_read_netstring(stream);
  fprintf(stream, "Status: 200 OK\r\nContent-Type: text/plain\r\n\r\n");
  while (buf->len){
    size_t itemlen = strlen(buf->ptr);
    fprintf(stream, "[%s]\n", buf->ptr);
    buf->len -= itemlen + 1;
    buf->ptr += itemlen + 1;
  }
}

int main(int argc, char**argv){
  int server_fd = tcp_bind(1337);
  int client_fd;

  while ((client_fd = accept(server_fd, NULL, NULL)) != -1){
    fprintf(stderr, "client_fd=%d\n", client_fd);
    FILE* stream = fdopen(client_fd, "r+");
    if (!stream){
      perror("fdopen");
    }
    scgi_read_headers(stream);
    fclose(stream);
  }
  perror("accept");
  return EXIT_FAILURE;
}