Method: Array#pack

Defined in:
pack.c

#pack(fmt) ⇒ Object

Packs the contents of arr into a binary sequence according to the directives in aTemplateString (see the table below) Directives “A,'' “a,'' and “Z'' may be followed by a count, which gives the width of the resulting field. The remaining directives also may take a count, indicating the number of array elements to convert. If the count is an asterisk (“*''), all remaining array elements will be converted. Any of the directives “sSiIlL'' may be followed by an underscore (“_'') or exclamation mark (“!'') to use the underlying platform's native size for the specified type; otherwise, they use a platform-independent size. Spaces are ignored in the template string. See also String#unpack.

a = [ "a", "b", "c" ]
n = [ 65, 66, 67 ]
a.pack("A3A3A3")   #=> "a  b  c  "
a.pack("a3a3a3")   #=> "a\000\000b\000\000c\000\000"
n.pack("ccc")      #=> "ABC"

Directives for pack.

Integer      | Array   |
Directive    | Element | Meaning
---------------------------------------------------------------------------
   C         | Integer | 8-bit unsigned (unsigned char)
   S         | Integer | 16-bit unsigned, native endian (uint16_t)
   L         | Integer | 32-bit unsigned, native endian (uint32_t)
   Q         | Integer | 64-bit unsigned, native endian (uint64_t)
   J         | Integer | pointer width unsigned, native endian (uintptr_t)
             |         | (J is available since Ruby 2.3.)
             |         |
   c         | Integer | 8-bit signed (signed char)
   s         | Integer | 16-bit signed, native endian (int16_t)
   l         | Integer | 32-bit signed, native endian (int32_t)
   q         | Integer | 64-bit signed, native endian (int64_t)
   j         | Integer | pointer width signed, native endian (intptr_t)
             |         | (j is available since Ruby 2.3.)
             |         |
   S_, S!    | Integer | unsigned short, native endian
   I, I_, I! | Integer | unsigned int, native endian
   L_, L!    | Integer | unsigned long, native endian
   Q_, Q!    | Integer | unsigned long long, native endian (ArgumentError
             |         | if the platform has no long long type.)
             |         | (Q_ and Q! is available since Ruby 2.1.)
   J!        | Integer | uintptr_t, native endian (same with J)
             |         | (J! is available since Ruby 2.3.)
             |         |
   s_, s!    | Integer | signed short, native endian
   i, i_, i! | Integer | signed int, native endian
   l_, l!    | Integer | signed long, native endian
   q_, q!    | Integer | signed long long, native endian (ArgumentError
             |         | if the platform has no long long type.)
             |         | (q_ and q! is available since Ruby 2.1.)
   j!        | Integer | intptr_t, native endian (same with j)
             |         | (j! is available since Ruby 2.3.)
             |         |
   S> L> Q>  | Integer | same as the directives without ">" except
   J> s> l>  |         | big endian
   q> j>     |         | (available since Ruby 1.9.3)
   S!> I!>   |         | "S>" is same as "n"
   L!> Q!>   |         | "L>" is same as "N"
   J!> s!>   |         |
   i!> l!>   |         |
   q!> j!>   |         |
             |         |
   S< L< Q<  | Integer | same as the directives without "<" except
   J< s< l<  |         | little endian
   q< j<     |         | (available since Ruby 1.9.3)
   S!< I!<   |         | "S<" is same as "v"
   L!< Q!<   |         | "L<" is same as "V"
   J!< s!<   |         |
   i!< l!<   |         |
   q!< j!<   |         |
             |         |
   n         | Integer | 16-bit unsigned, network (big-endian) byte order
   N         | Integer | 32-bit unsigned, network (big-endian) byte order
   v         | Integer | 16-bit unsigned, VAX (little-endian) byte order
   V         | Integer | 32-bit unsigned, VAX (little-endian) byte order
             |         |
   U         | Integer | UTF-8 character
   w         | Integer | BER-compressed integer

Float        |         |
Directive    |         | Meaning
---------------------------------------------------------------------------
   D, d      | Float   | double-precision, native format
   F, f      | Float   | single-precision, native format
   E         | Float   | double-precision, little-endian byte order
   e         | Float   | single-precision, little-endian byte order
   G         | Float   | double-precision, network (big-endian) byte order
   g         | Float   | single-precision, network (big-endian) byte order

String       |         |
Directive    |         | Meaning
---------------------------------------------------------------------------
   A         | String  | arbitrary binary string (space padded, count is width)
   a         | String  | arbitrary binary string (null padded, count is width)
   Z         | String  | same as ``a'', except that null is added with *
   B         | String  | bit string (MSB first)
   b         | String  | bit string (LSB first)
   H         | String  | hex string (high nibble first)
   h         | String  | hex string (low nibble first)
   u         | String  | UU-encoded string
   M         | String  | quoted printable, MIME encoding (see RFC2045)
   m         | String  | base64 encoded string (see RFC 2045, count is width)
             |         | (if count is 0, no line feed are added, see RFC 4648)
   P         | String  | pointer to a structure (fixed-length string)
   p         | String  | pointer to a null-terminated string

Misc.        |         |
Directive    |         | Meaning
---------------------------------------------------------------------------
   @         | ---     | moves to absolute position
   X         | ---     | back up a byte
   x         | ---     | null byte


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# File 'pack.c', line 356

static VALUE
pack_pack(VALUE ary, VALUE fmt)
{
    static const char nul10[] = "\0\0\0\0\0\0\0\0\0\0";
    static const char spc10[] = "          ";
    const char *p, *pend;
    VALUE res, from, associates = 0;
    char type;
    long len, idx, plen;
    const char *ptr;
    int enc_info = 1;   /* 0 - BINARY, 1 - US-ASCII, 2 - UTF-8 */
#ifdef NATINT_PACK
    int natint;   /* native integer */
#endif
    int integer_size, bigendian_p;

    StringValue(fmt);
    p = RSTRING_PTR(fmt);
    pend = p + RSTRING_LEN(fmt);
    res = rb_str_buf_new(0);

    idx = 0;

#define TOO_FEW (rb_raise(rb_eArgError, toofew), 0)
#define MORE_ITEM (idx < RARRAY_LEN(ary))
#define THISFROM (MORE_ITEM ? RARRAY_AREF(ary, idx) : TOO_FEW)
#define NEXTFROM (MORE_ITEM ? RARRAY_AREF(ary, idx++) : TOO_FEW)

    while (p < pend) {
  int explicit_endian = 0;
  if (RSTRING_PTR(fmt) + RSTRING_LEN(fmt) != pend) {
      rb_raise(rb_eRuntimeError, "format string modified");
  }
  type = *p++;   /* get data type */
#ifdef NATINT_PACK
  natint = 0;
#endif

  if (ISSPACE(type)) continue;
  if (type == '#') {
      while ((p < pend) && (*p != '\n')) {
    p++;
      }
      continue;
  }

  {
          modifiers:
      switch (*p) {
        case '_':
        case '!':
    if (strchr(natstr, type)) {
#ifdef NATINT_PACK
        natint = 1;
#endif
        p++;
    }
    else {
        rb_raise(rb_eArgError, "'%c' allowed only after types %s", *p, natstr);
    }
    goto modifiers;

        case '<':
        case '>':
    if (!strchr(endstr, type)) {
        rb_raise(rb_eArgError, "'%c' allowed only after types %s", *p, endstr);
    }
    if (explicit_endian) {
        rb_raise(rb_eRangeError, "Can't use both '<' and '>'");
    }
    explicit_endian = *p++;
    goto modifiers;
      }
  }

  if (*p == '*') { /* set data length */
      len = strchr("@Xxu", type) ? 0
                : strchr("PMm", type) ? 1
                : RARRAY_LEN(ary) - idx;
      p++;
  }
  else if (ISDIGIT(*p)) {
      errno = 0;
      len = STRTOUL(p, (char**)&p, 10);
      if (errno) {
    rb_raise(rb_eRangeError, "pack length too big");
      }
  }
  else {
      len = 1;
  }

  switch (type) {
    case 'U':
      /* if encoding is US-ASCII, upgrade to UTF-8 */
      if (enc_info == 1) enc_info = 2;
      break;
    case 'm': case 'M': case 'u':
      /* keep US-ASCII (do nothing) */
      break;
    default:
      /* fall back to BINARY */
      enc_info = 0;
      break;
  }
  switch (type) {
    case 'A': case 'a': case 'Z':
    case 'B': case 'b':
    case 'H': case 'h':
      from = NEXTFROM;
      if (NIL_P(from)) {
    ptr = "";
    plen = 0;
      }
      else {
    StringValue(from);
    ptr = RSTRING_PTR(from);
    plen = RSTRING_LEN(from);
    OBJ_INFECT(res, from);
      }

      if (p[-1] == '*')
    len = plen;

      switch (type) {
        case 'a':    /* arbitrary binary string (null padded)  */
        case 'A':         /* arbitrary binary string (ASCII space padded) */
        case 'Z':         /* null terminated string  */
    if (plen >= len) {
        rb_str_buf_cat(res, ptr, len);
        if (p[-1] == '*' && type == 'Z')
      rb_str_buf_cat(res, nul10, 1);
    }
    else {
        rb_str_buf_cat(res, ptr, plen);
        len -= plen;
        while (len >= 10) {
      rb_str_buf_cat(res, (type == 'A')?spc10:nul10, 10);
      len -= 10;
        }
        rb_str_buf_cat(res, (type == 'A')?spc10:nul10, len);
    }
    break;

#define castchar(from) (char)((from) & 0xff)

        case 'b':    /* bit string (ascending) */
    {
        int byte = 0;
        long i, j = 0;

        if (len > plen) {
      j = (len - plen + 1)/2;
      len = plen;
        }
        for (i=0; i++ < len; ptr++) {
      if (*ptr & 1)
          byte |= 128;
      if (i & 7)
          byte >>= 1;
      else {
          char c = castchar(byte);
          rb_str_buf_cat(res, &c, 1);
          byte = 0;
      }
        }
        if (len & 7) {
      char c;
      byte >>= 7 - (len & 7);
      c = castchar(byte);
      rb_str_buf_cat(res, &c, 1);
        }
        len = j;
        goto grow;
    }
    break;

        case 'B':    /* bit string (descending) */
    {
        int byte = 0;
        long i, j = 0;

        if (len > plen) {
      j = (len - plen + 1)/2;
      len = plen;
        }
        for (i=0; i++ < len; ptr++) {
      byte |= *ptr & 1;
      if (i & 7)
          byte <<= 1;
      else {
          char c = castchar(byte);
          rb_str_buf_cat(res, &c, 1);
          byte = 0;
      }
        }
        if (len & 7) {
      char c;
      byte <<= 7 - (len & 7);
      c = castchar(byte);
      rb_str_buf_cat(res, &c, 1);
        }
        len = j;
        goto grow;
    }
    break;

        case 'h':    /* hex string (low nibble first) */
    {
        int byte = 0;
        long i, j = 0;

        if (len > plen) {
      j = (len + 1) / 2 - (plen + 1) / 2;
      len = plen;
        }
        for (i=0; i++ < len; ptr++) {
      if (ISALPHA(*ptr))
          byte |= (((*ptr & 15) + 9) & 15) << 4;
      else
          byte |= (*ptr & 15) << 4;
      if (i & 1)
          byte >>= 4;
      else {
          char c = castchar(byte);
          rb_str_buf_cat(res, &c, 1);
          byte = 0;
      }
        }
        if (len & 1) {
      char c = castchar(byte);
      rb_str_buf_cat(res, &c, 1);
        }
        len = j;
        goto grow;
    }
    break;

        case 'H':    /* hex string (high nibble first) */
    {
        int byte = 0;
        long i, j = 0;

        if (len > plen) {
      j = (len + 1) / 2 - (plen + 1) / 2;
      len = plen;
        }
        for (i=0; i++ < len; ptr++) {
      if (ISALPHA(*ptr))
          byte |= ((*ptr & 15) + 9) & 15;
      else
          byte |= *ptr & 15;
      if (i & 1)
          byte <<= 4;
      else {
          char c = castchar(byte);
          rb_str_buf_cat(res, &c, 1);
          byte = 0;
      }
        }
        if (len & 1) {
      char c = castchar(byte);
      rb_str_buf_cat(res, &c, 1);
        }
        len = j;
        goto grow;
    }
    break;
      }
      break;

    case 'c':    /* signed char */
    case 'C':    /* unsigned char */
            integer_size = 1;
            bigendian_p = BIGENDIAN_P(); /* not effective */
            goto pack_integer;

    case 's':    /* s for int16_t, s! for signed short */
            integer_size = NATINT_LEN(short, 2);
            bigendian_p = BIGENDIAN_P();
            goto pack_integer;

    case 'S':    /* S for uint16_t, S! for unsigned short */
            integer_size = NATINT_LEN(short, 2);
            bigendian_p = BIGENDIAN_P();
            goto pack_integer;

    case 'i':    /* i and i! for signed int */
            integer_size = (int)sizeof(int);
            bigendian_p = BIGENDIAN_P();
            goto pack_integer;

    case 'I':    /* I and I! for unsigned int */
            integer_size = (int)sizeof(int);
            bigendian_p = BIGENDIAN_P();
            goto pack_integer;

    case 'l':    /* l for int32_t, l! for signed long */
            integer_size = NATINT_LEN(long, 4);
            bigendian_p = BIGENDIAN_P();
            goto pack_integer;

    case 'L':    /* L for uint32_t, L! for unsigned long */
            integer_size = NATINT_LEN(long, 4);
            bigendian_p = BIGENDIAN_P();
            goto pack_integer;

    case 'q':    /* q for int64_t, q! for signed long long */
      integer_size = NATINT_LEN_Q;
            bigendian_p = BIGENDIAN_P();
            goto pack_integer;

    case 'Q':    /* Q for uint64_t, Q! for unsigned long long */
      integer_size = NATINT_LEN_Q;
            bigendian_p = BIGENDIAN_P();
            goto pack_integer;

    case 'j':    /* j for intptr_t */
      integer_size = sizeof(intptr_t);
      bigendian_p = BIGENDIAN_P();
      goto pack_integer;

    case 'J':    /* J for uintptr_t */
      integer_size = sizeof(uintptr_t);
      bigendian_p = BIGENDIAN_P();
      goto pack_integer;

    case 'n':    /* 16 bit (2 bytes) integer (network byte-order)  */
            integer_size = 2;
            bigendian_p = 1;
            goto pack_integer;

    case 'N':    /* 32 bit (4 bytes) integer (network byte-order) */
            integer_size = 4;
            bigendian_p = 1;
            goto pack_integer;

    case 'v':    /* 16 bit (2 bytes) integer (VAX byte-order) */
            integer_size = 2;
            bigendian_p = 0;
            goto pack_integer;

    case 'V':    /* 32 bit (4 bytes) integer (VAX byte-order) */
            integer_size = 4;
            bigendian_p = 0;
            goto pack_integer;

          pack_integer:
      if (explicit_endian) {
    bigendian_p = explicit_endian == '>';
      }
            if (integer_size > MAX_INTEGER_PACK_SIZE)
                rb_bug("unexpected intger size for pack: %d", integer_size);
            while (len-- > 0) {
                char intbuf[MAX_INTEGER_PACK_SIZE];

                from = NEXTFROM;
                rb_integer_pack(from, intbuf, integer_size, 1, 0,
                    INTEGER_PACK_2COMP |
                    (bigendian_p ? INTEGER_PACK_BIG_ENDIAN : INTEGER_PACK_LITTLE_ENDIAN));
                rb_str_buf_cat(res, intbuf, integer_size);
            }
      break;

    case 'f':    /* single precision float in native format */
    case 'F':    /* ditto */
      while (len-- > 0) {
    float f;

    from = NEXTFROM;
    f = (float)RFLOAT_VALUE(rb_to_float(from));
    rb_str_buf_cat(res, (char*)&f, sizeof(float));
      }
      break;

    case 'e':    /* single precision float in VAX byte-order */
      while (len-- > 0) {
    float f;
    FLOAT_CONVWITH(ftmp);

    from = NEXTFROM;
    f = (float)RFLOAT_VALUE(rb_to_float(from));
    f = HTOVF(f,ftmp);
    rb_str_buf_cat(res, (char*)&f, sizeof(float));
      }
      break;

    case 'E':    /* double precision float in VAX byte-order */
      while (len-- > 0) {
    double d;
    DOUBLE_CONVWITH(dtmp);

    from = NEXTFROM;
    d = RFLOAT_VALUE(rb_to_float(from));
    d = HTOVD(d,dtmp);
    rb_str_buf_cat(res, (char*)&d, sizeof(double));
      }
      break;

    case 'd':    /* double precision float in native format */
    case 'D':    /* ditto */
      while (len-- > 0) {
    double d;

    from = NEXTFROM;
    d = RFLOAT_VALUE(rb_to_float(from));
    rb_str_buf_cat(res, (char*)&d, sizeof(double));
      }
      break;

    case 'g':    /* single precision float in network byte-order */
      while (len-- > 0) {
    float f;
    FLOAT_CONVWITH(ftmp);

    from = NEXTFROM;
    f = (float)RFLOAT_VALUE(rb_to_float(from));
    f = HTONF(f,ftmp);
    rb_str_buf_cat(res, (char*)&f, sizeof(float));
      }
      break;

    case 'G':    /* double precision float in network byte-order */
      while (len-- > 0) {
    double d;
    DOUBLE_CONVWITH(dtmp);

    from = NEXTFROM;
    d = RFLOAT_VALUE(rb_to_float(from));
    d = HTOND(d,dtmp);
    rb_str_buf_cat(res, (char*)&d, sizeof(double));
      }
      break;

    case 'x':    /* null byte */
    grow:
      while (len >= 10) {
    rb_str_buf_cat(res, nul10, 10);
    len -= 10;
      }
      rb_str_buf_cat(res, nul10, len);
      break;

    case 'X':    /* back up byte */
    shrink:
      plen = RSTRING_LEN(res);
      if (plen < len)
    rb_raise(rb_eArgError, "X outside of string");
      rb_str_set_len(res, plen - len);
      break;

    case '@':    /* null fill to absolute position */
      len -= RSTRING_LEN(res);
      if (len > 0) goto grow;
      len = -len;
      if (len > 0) goto shrink;
      break;

    case '%':
      rb_raise(rb_eArgError, "%% is not supported");
      break;

    case 'U':    /* Unicode character */
      while (len-- > 0) {
    SIGNED_VALUE l;
    char buf[8];
    int le;

    from = NEXTFROM;
    from = rb_to_int(from);
    l = NUM2LONG(from);
    if (l < 0) {
        rb_raise(rb_eRangeError, "pack(U): value out of range");
    }
    le = rb_uv_to_utf8(buf, l);
    rb_str_buf_cat(res, (char*)buf, le);
      }
      break;

    case 'u':    /* uuencoded string */
    case 'm':    /* base64 encoded string */
      from = NEXTFROM;
      StringValue(from);
      ptr = RSTRING_PTR(from);
      plen = RSTRING_LEN(from);

      if (len == 0 && type == 'm') {
    encodes(res, ptr, plen, type, 0);
    ptr += plen;
    break;
      }
      if (len <= 2)
    len = 45;
      else if (len > 63 && type == 'u')
    len = 63;
      else
    len = len / 3 * 3;
      while (plen > 0) {
    long todo;

    if (plen > len)
        todo = len;
    else
        todo = plen;
    encodes(res, ptr, todo, type, 1);
    plen -= todo;
    ptr += todo;
      }
      break;

    case 'M':    /* quoted-printable encoded string */
      from = rb_obj_as_string(NEXTFROM);
      if (len <= 1)
    len = 72;
      qpencode(res, from, len);
      break;

    case 'P':    /* pointer to packed byte string */
      from = THISFROM;
      if (!NIL_P(from)) {
    StringValue(from);
    if (RSTRING_LEN(from) < len) {
        rb_raise(rb_eArgError, "too short buffer for P(%ld for %ld)",
           RSTRING_LEN(from), len);
    }
      }
      len = 1;
      /* FALL THROUGH */
    case 'p':    /* pointer to string */
      while (len-- > 0) {
    char *t;
    from = NEXTFROM;
    if (NIL_P(from)) {
        t = 0;
    }
    else {
        t = StringValuePtr(from);
        rb_obj_taint(from);
    }
    if (!associates) {
        associates = rb_ary_new();
    }
    rb_ary_push(associates, from);
    rb_str_buf_cat(res, (char*)&t, sizeof(char*));
      }
      break;

    case 'w':    /* BER compressed integer  */
      while (len-- > 0) {
    VALUE buf = rb_str_new(0, 0);
                size_t numbytes;
                int sign;
                char *cp;

    from = NEXTFROM;
                from = rb_to_int(from);
                numbytes = rb_absint_numwords(from, 7, NULL);
                if (numbytes == 0)
                    numbytes = 1;
                buf = rb_str_new(NULL, numbytes);

                sign = rb_integer_pack(from, RSTRING_PTR(buf), RSTRING_LEN(buf), 1, 1, INTEGER_PACK_BIG_ENDIAN);

                if (sign < 0)
                    rb_raise(rb_eArgError, "can't compress negative numbers");
                if (sign == 2)
                    rb_bug("buffer size problem?");

                cp = RSTRING_PTR(buf);
                while (1 < numbytes) {
                  *cp |= 0x80;
                  cp++;
                  numbytes--;
                }

                rb_str_buf_cat(res, RSTRING_PTR(buf), RSTRING_LEN(buf));
      }
      break;

    default: {
      char unknown[5];
      if (ISPRINT(type)) {
    unknown[0] = type;
    unknown[1] = '\0';
      }
      else {
    snprintf(unknown, sizeof(unknown), "\\x%.2x", type & 0xff);
      }
      rb_warning("unknown pack directive '%s' in '% "PRIsVALUE"'",
           unknown, fmt);
      break;
    }
  }
    }

    if (associates) {
  str_associate(res, associates);
    }
    OBJ_INFECT(res, fmt);
    switch (enc_info) {
      case 1:
  ENCODING_CODERANGE_SET(res, rb_usascii_encindex(), ENC_CODERANGE_7BIT);
  break;
      case 2:
  rb_enc_set_index(res, rb_utf8_encindex());
  break;
      default:
  /* do nothing, keep ASCII-8BIT */
  break;
    }
    return res;
}