/* uudecode.c - uudecode / base64 decode
 *
 * Copyright 2013 Erich Plondke <toybox@erich.wreck.org>
 *
 * See http://pubs.opengroup.org/onlinepubs/9699919799/utilities/uudecode.html

USE_UUENCODE(NEWTOY(uudecode, ">2o:", TOYFLAG_USR|TOYFLAG_BIN))

config UUDECODE
  bool "uudecode"
  default n
  help
    usage: uudecode [-o outfile] [file]

    Uudecode or base64-decode stdin or [file], sending output to outfile or
    filename specified by input.
*/

#define FOR_uudecode
#include "toys.h"

GLOBALS(
  char *o;
)

/*
 * Turn a character back into a value.
 * The smallest valid character is 0x2B ('+')
 * The biggest valid character is 0x7A ('z')
 * We can make a table of 16*5 entries to cover 0x2B - 0x7A
 */

static inline int startswith(const char *a, const char *b)
{
	return (0==strncmp(a,b,strlen(b)));
}

static inline signed char uudecode_b64_1byte(char in)
{
  char ret;
  static const signed char table[16*5] = {
    /* '+' (0x2B) is 62, '/'(0x2F) is 63, rest invalid */
                                                62, -1, -1, -1, 63,
    /* '0'-'9' are values 52-61, rest of 0x3A - 0x3F is invalid, = is special... */
    52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,
    /* '@' is invalid, 'A'-'Z' are values 0-25, 0x5b - 0x5F are invalid */
    -1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
    15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
    /* '`' is invalid, 'a'-'z' are values 26-51, 0x7B - 0x7F are invalid */
    -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
    41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51
  };
  in &= 0x7f;
  if (in < '+') return -1;
  if (in > 'z') return -1;
  in -= '+';
  ret = table[in];
  return ret;
};


/* Returns length put in out */
static int uudecode_b64_4bytes(char *out, const char *in)
{
  unsigned int i,x=0;
  signed char b0,b1,b2,b3;
  int len = 3;
  b0 = uudecode_b64_1byte(in[0]);
  b1 = uudecode_b64_1byte(in[1]);
  b2 = uudecode_b64_1byte(in[2]);
  b3 = uudecode_b64_1byte(in[3]);
  if ((b1 < 0) || (b0 < 0)) return 0;
  if (b3 < 0) len--;
  if (b2 < 0) len--;
  x = ((b0 & 0x3f)<<18) | ((b1 & 0x3f)<<12) | ((b2 & 0x3f) << 6) | (b3 & 0x3f);
  for (i = 0; i < len; i++) {
    *out++ = (x>>(8*(2-i))) & 0x0ff;
  }
  return len;
}

static void uudecode_b64_line(int ofd, const char *in, int ilen)
{
  int olen;
  char out[4];
  while (ilen >= 4) {
    olen = uudecode_b64_4bytes(out,in);
    xwrite(ofd,out,olen);
    in += 4;
    ilen -= 4;
  };
}

static void uudecode_b64(int ifd, int ofd)
{
  int len;
  char *line;
  while ((line = get_line(ifd)) != NULL) {
    if (startswith(line,"====")) return;
    if ((len = strlen(line)) < 4) continue; // skip empty lines
    uudecode_b64_line(ofd,line,len);
    free(line);
  }
}


static void uudecode_uu_4bytes(char *out, const char *in, int len)
{
  unsigned int i,x=0;
  for (i = 0; i < 4; i++) {
    x |= ((in[i] - 32) & 0x03f) << (6*(3-i));
  }
  if (len > 3) len = 3;
  for (i = 0; i < len; i++) {
    *out++ = x >> (8*(2-i));
  }
}

static void uudecode_uu_line(int ofd, const char *in)
{
  int olen = in[0] - 32;
  char buf[4];
  in++;
  while (olen > 0) {
    uudecode_uu_4bytes(buf,in,olen);
    xwrite(ofd,buf,olen < 3 ? olen : 3);
    olen -= 3;
    in += 4;
  }
}

static void uudecode_uu(int ifd, int ofd)
{
  char *line = NULL;
  while ((line = get_line(ifd)) != NULL) {
    if (line[0] == '`') break;
    if (startswith(line,"end")) break;
    if (strlen(line) < 1) break;
    uudecode_uu_line(ofd,line);
    free(line);
  }
}

void uudecode_main(void)
{
  char *out_filename = NULL;
  int ifd = 0; /* STDIN */
  int ofd = 1; /* STDOUT */
  char *line;
  char *p,*p2;
  void (*decoder)(int ifd, int ofd) = NULL;
  long mode = 0744;
  if (toys.optc == 1) {
    ifd = xopen(toys.optargs[0],O_RDONLY); // dies if error
  }
  do {
    if ((line = get_line(ifd)) == NULL) perror_exit("empty file");
  } while (strlen(line) == 0); /* skip over empty lines */ 
  if (startswith(line,"begin ")) decoder = uudecode_uu;
  else if (startswith(line,"begin-base64 ")) decoder = uudecode_b64;
  else perror_exit("not a valid uu- or base64-encoded file");
  for (p = line; !isspace(*p); p++) /* skip first part */;
  for (; isspace(*p); p++) /* skip spaces */;
  mode = strtoul(p,&p2,8);
  p = p2 + 1; /* skip space */
  if (toys.optflags & FLAG_o) {
    out_filename = TT.o;
  } else {
    out_filename = p;
  }
  ofd = xcreate(out_filename,O_WRONLY|O_CREAT|O_TRUNC,mode);
  free(line);
  decoder(ifd,ofd);
  if (TOYBOX_CLEANUP) close(ofd);
}