text: /*
   * Copyright (c) 2014, Google Inc.
   *
   * Permission to use, copy, modify, and/or distribute this software for any
   * purpose with or without fee is hereby granted, provided that the above
   * copyright notice and this permission notice appear in all copies.
   *
   * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
   * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
   * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
   * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
   * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
   * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
   */
  
  #include <assert.h>
  #include <stdlib.h>
  #include <string.h>
  
  #include <openssl/opensslconf.h>
  
  #include "bytestring.h"
  
  static int cbb_init(CBB *cbb, uint8_t *buf, size_t cap)
  {
      struct cbb_buffer_st *base;
  
      base = malloc(sizeof(struct cbb_buffer_st));
      if (base == NULL)
          return 0;
  
      base->buf = buf;
      base->len = 0;
      base->cap = cap;
      base->can_resize = 1;
  
      memset(cbb, 0, sizeof(CBB));
      cbb->base = base;
      cbb->is_top_level = 1;
      return 1;
  }
  
  int CBB_init(CBB *cbb, size_t initial_capacity)
  {
      uint8_t *buf;
  
      buf = malloc(initial_capacity);
      if (initial_capacity > 0 && buf == NULL)
          return 0;
  
      if (!cbb_init(cbb, buf, initial_capacity)) {
          free(buf);
          return 0;
      }
  
      return 1;
  }
  
  int CBB_init_fixed(CBB *cbb, uint8_t *buf, size_t len)
  {
      if (!cbb_init(cbb, buf, len))
          return 0;
  
      cbb->base->can_resize = 0;
      return 1;
  }
  
  void CBB_cleanup(CBB *cbb)
  {
      if (cbb->base) {
          if (cbb->base->buf && cbb->base->can_resize)
              free(cbb->base->buf);
          free(cbb->base);
      }
      cbb->base = NULL;
  }
  
  static int cbb_buffer_add(struct cbb_buffer_st *base, uint8_t **out, size_t len)
  {
      size_t newlen;
  
      if (base == NULL)
          return 0;
  
      newlen = base->len + len;
      if (newlen < base->len)
          /* Overflow */
          return 0;
  
      if (newlen > base->cap) {
          size_t newcap = base->cap * 2;
          uint8_t *newbuf;
  
          if (!base->can_resize)
              return 0;
  
          if (newcap < base->cap || newcap < newlen)
              newcap = newlen;
  
          newbuf = realloc(base->buf, newcap);
          if (newbuf == NULL)
              return 0;
  
          base->buf = newbuf;
          base->cap = newcap;
      }
  
      if (out)
          *out = base->buf + base->len;
      
      base->len = newlen;
      return 1;
  }
  
  static int cbb_buffer_add_u(struct cbb_buffer_st *base, uint32_t v, size_t len_len)
  {
      uint8_t *buf;
      size_t i;
  
      if (len_len == 0)
          return 1;
  
      if (!cbb_buffer_add(base, &buf, len_len))
          return 0;
  
      for (i = len_len - 1; i < len_len; i--) {
          buf[i] = v;
          v >>= 8;
      }
      return 1;
  }
  
  int CBB_finish(CBB *cbb, uint8_t **out_data, size_t *out_len)
  {
      if (!cbb->is_top_level)
          return 0;
  
      if (!CBB_flush(cbb))
          return 0;
  
      if (cbb->base->can_resize && (out_data == NULL || out_len == NULL))
          /* |out_data| and |out_len| can only be NULL if the CBB is fixed. */
          return 0;
  
      if (out_data != NULL)
          *out_data = cbb->base->buf;
      if (out_len != NULL)
          *out_len = cbb->base->len;
  
      cbb->base->buf = NULL;
      CBB_cleanup(cbb);
      return 1;
  }
  
  /* CBB_flush recurses and then writes out any pending length prefix. The
   * current length of the underlying base is taken to be the length of the
   * length-prefixed data. */
  int CBB_flush(CBB *cbb)
  {
      size_t child_start, i, len;
  
      if (cbb->base == NULL)
          return 0;
  
      if (cbb->child == NULL || cbb->pending_len_len == 0)
          return 1;
  
      child_start = cbb->offset + cbb->pending_len_len;
  
      if (!CBB_flush(cbb->child) || child_start < cbb->offset ||
          cbb->base->len < child_start)
          return 0;
  
      len = cbb->base->len - child_start;
  
      if (cbb->pending_is_asn1) {
          /*
           * For ASN.1 we assume that we'll only need a single byte for the length.
           * If that turned out to be incorrect, we have to move the contents along
           * in order to make space.
           */
          size_t len_len;
          uint8_t initial_length_byte;
  
          assert(cbb->pending_len_len == 1);
  
          if (len > 0xfffffffe) {
              /* Too large. */
              return 0;
          } else if (len > 0xffffff) {
              len_len = 5;
              initial_length_byte = 0x80 | 4;
          } else if (len > 0xffff) {
              len_len = 4;
              initial_length_byte = 0x80 | 3;
          } else if (len > 0xff) {
              len_len = 3;
              initial_length_byte = 0x80 | 2;
          } else if (len > 0x7f) {
              len_len = 2;
              initial_length_byte = 0x80 | 1;
          } else {
              len_len = 1;
              initial_length_byte = len;
              len = 0;
          }
  
          if (len_len != 1) {
              /* We need to move the contents along in order to make space. */
              size_t extra_bytes = len_len - 1;
              if (!cbb_buffer_add(cbb->base, NULL, extra_bytes))
                  return 0;
  
              memmove(cbb->base->buf + child_start + extra_bytes,
                      cbb->base->buf + child_start, len);
          }
          cbb->base->buf[cbb->offset++] = initial_length_byte;
          cbb->pending_len_len = len_len - 1;
      }
  
      for (i = cbb->pending_len_len - 1; i < cbb->pending_len_len; i--) {
          cbb->base->buf[cbb->offset + i] = len;
          len >>= 8;
      }
      if (len != 0)
          return 0;
  
      cbb->child->base = NULL;
      cbb->child = NULL;
      cbb->pending_len_len = 0;
      cbb->pending_is_asn1 = 0;
      cbb->offset = 0;
  
      return 1;
  }
  
  static int cbb_add_length_prefixed(CBB *cbb, CBB *out_contents, size_t len_len)
  {
      uint8_t *prefix_bytes;
  
      if (!CBB_flush(cbb))
          return 0;
  
      cbb->offset = cbb->base->len;
      if (!cbb_buffer_add(cbb->base, &prefix_bytes, len_len))
          return 0;
  
      memset(prefix_bytes, 0, len_len);
      memset(out_contents, 0, sizeof(CBB));
      out_contents->base = cbb->base;
      cbb->child = out_contents;
      cbb->pending_len_len = len_len;
      cbb->pending_is_asn1 = 0;
  
      return 1;
  }
  
  int CBB_add_u8_length_prefixed(CBB *cbb, CBB *out_contents)
  {
      return cbb_add_length_prefixed(cbb, out_contents, 1);
  }
  
  int CBB_add_u16_length_prefixed(CBB *cbb, CBB *out_contents)
  {
      return cbb_add_length_prefixed(cbb, out_contents, 2);
  }
  
  int CBB_add_u24_length_prefixed(CBB *cbb, CBB *out_contents)
  {
      return cbb_add_length_prefixed(cbb, out_contents, 3);
  }
  
  int CBB_add_asn1(CBB *cbb, CBB *out_contents, uint8_t tag)
  {
      if ((tag & 0x1f) == 0x1f)
          /* Long form identifier octets are not supported. */
          return 0;
  
      if (!CBB_flush(cbb) || !CBB_add_u8(cbb, tag))
          return 0;
  
      cbb->offset = cbb->base->len;
      if (!CBB_add_u8(cbb, 0))
          return 0;
  
      memset(out_contents, 0, sizeof(CBB));
      out_contents->base = cbb->base;
      cbb->child = out_contents;
      cbb->pending_len_len = 1;
      cbb->pending_is_asn1 = 1;
  
      return 1;
  }
  
  int CBB_add_bytes(CBB *cbb, const uint8_t *data, size_t len)
  {
      uint8_t *dest;
  
      if (!CBB_flush(cbb) || !cbb_buffer_add(cbb->base, &dest, len))
          return 0;
  
      memcpy(dest, data, len);
      return 1;
  }
  
  int CBB_add_space(CBB *cbb, uint8_t **out_data, size_t len)
  {
      if (!CBB_flush(cbb) || !cbb_buffer_add(cbb->base, out_data, len))
          return 0;
  
      return 1;
  }
  
  int CBB_add_u8(CBB *cbb, uint8_t value)
  {
      if (!CBB_flush(cbb))
          return 0;
  
      return cbb_buffer_add_u(cbb->base, value, 1);
  }
  
  int CBB_add_u16(CBB *cbb, uint16_t value)
  {
      if (!CBB_flush(cbb))
          return 0;
  
      return cbb_buffer_add_u(cbb->base, value, 2);
  }
  
  int CBB_add_u24(CBB *cbb, uint32_t value)
  {
      if (!CBB_flush(cbb))
          return 0;
  
      return cbb_buffer_add_u(cbb->base, value, 3);
  }
  
  int CBB_add_asn1_uint64(CBB *cbb, uint64_t value)
  {
      CBB child;
      size_t i;
      int started = 0;
  
      if (!CBB_add_asn1(cbb, &child, CBS_ASN1_INTEGER))
          return 0;
  
      for (i = 0; i < 8; i++) {
          uint8_t byte = (value >> 8 * (7 - i)) & 0xff;
          if (!started) {
              if (byte == 0)
                  /* Don't encode leading zeros. */
                  continue;
              /*
               * If the high bit is set, add a padding byte to make it
               * unsigned.
               */
              if ((byte & 0x80) && !CBB_add_u8(&child, 0))
                  return 0;
  
              started = 1;
          }
          if (!CBB_add_u8(&child, byte))
              return 0;
      }
  
      /* 0 is encoded as a single 0, not the empty string. */
      if (!started && !CBB_add_u8(&child, 0))
          return 0;
  
      return CBB_flush(cbb);
  }
  