/*
 * checksum.c:   checksum routines
 *
 * ====================================================================
 * Copyright (c) 2008 CollabNet.  All rights reserved.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution.  The terms
 * are also available at http://subversion.tigris.org/license-1.html.
 * If newer versions of this license are posted there, you may use a
 * newer version instead, at your option.
 *
 * This software consists of voluntary contributions made by many
 * individuals.  For exact contribution history, see the revision
 * history and logs, available at http://subversion.tigris.org/.
 * ====================================================================
 */


#include <ctype.h>

#include <apr_md5.h>
#include <apr_sha1.h>

#include "svn_checksum.h"
#include "svn_error.h"

#include "sha1.h"
#include "md5.h"



/* Returns the digest size of it's argument. */
#define DIGESTSIZE(k) ((k) == svn_checksum_md5 ? APR_MD5_DIGESTSIZE : \
                       (k) == svn_checksum_sha1 ? APR_SHA1_DIGESTSIZE : 0)


/* Check to see if KIND is something we recognize.  If not, return
 * SVN_ERR_BAD_CHECKSUM_KIND */
static svn_error_t *
validate_kind(svn_checksum_kind_t kind)
{
  if (kind == svn_checksum_md5 || kind == svn_checksum_sha1)
    return SVN_NO_ERROR;
  else
    return svn_error_create(SVN_ERR_BAD_CHECKSUM_KIND, NULL, NULL);
}


svn_checksum_t *
svn_checksum_create(svn_checksum_kind_t kind,
                    apr_pool_t *pool)
{
  svn_checksum_t *checksum;

  switch (kind)
    {
      case svn_checksum_md5:
      case svn_checksum_sha1:
        checksum = apr_pcalloc(pool, sizeof(*checksum) + DIGESTSIZE(kind));
        checksum->digest = (unsigned char *)checksum + sizeof(*checksum);
        checksum->kind = kind;
        return checksum;

      default:
        return NULL;
    }
}

svn_checksum_t *
svn_checksum__from_digest(const unsigned char *digest,
                          svn_checksum_kind_t kind,
                          apr_pool_t *result_pool)
{
  svn_checksum_t *checksum = svn_checksum_create(kind, result_pool);

  memcpy((unsigned char *)checksum->digest, digest, DIGESTSIZE(kind));
  return checksum;
}

svn_error_t *
svn_checksum_clear(svn_checksum_t *checksum)
{
  SVN_ERR(validate_kind(checksum->kind));

  memset((unsigned char *) checksum->digest, 0, DIGESTSIZE(checksum->kind));
  return SVN_NO_ERROR;
}

svn_boolean_t
svn_checksum_match(const svn_checksum_t *checksum1,
                   const svn_checksum_t *checksum2)
{
  if (checksum1 == NULL || checksum2 == NULL)
    return TRUE;

  if (checksum1->kind != checksum2->kind)
    return FALSE;

  switch (checksum1->kind)
    {
      case svn_checksum_md5:
        return svn_md5__digests_match(checksum1->digest, checksum2->digest);
      case svn_checksum_sha1:
        return svn_sha1__digests_match(checksum1->digest, checksum2->digest);
      default:
        /* We really shouldn't get here, but if we do... */
        return FALSE;
    }
}

const char *
svn_checksum_to_cstring_display(const svn_checksum_t *checksum,
                                apr_pool_t *pool)
{
  switch (checksum->kind)
    {
      case svn_checksum_md5:
        return svn_md5__digest_to_cstring_display(checksum->digest, pool);
      case svn_checksum_sha1:
        return svn_sha1__digest_to_cstring_display(checksum->digest, pool);
      default:
        /* We really shouldn't get here, but if we do... */
        return NULL;
    }
}

const char *
svn_checksum_to_cstring(const svn_checksum_t *checksum,
                        apr_pool_t *pool)
{
  switch (checksum->kind)
    {
      case svn_checksum_md5:
        return svn_md5__digest_to_cstring(checksum->digest, pool);
      case svn_checksum_sha1:
        return svn_sha1__digest_to_cstring(checksum->digest, pool);
      default:
        /* We really shouldn't get here, but if we do... */
        return NULL;
    }
}

svn_error_t *
svn_checksum_parse_hex(svn_checksum_t **checksum,
                       svn_checksum_kind_t kind,
                       const char *hex,
                       apr_pool_t *pool)
{
  int len;
  int i;
  unsigned char is_zeros = '\0';

  if (hex == NULL)
    {
      *checksum = NULL;
      return SVN_NO_ERROR;
    }

  SVN_ERR(validate_kind(kind));

  *checksum = svn_checksum_create(kind, pool);
  len = DIGESTSIZE(kind);

  for (i = 0; i < len; i++)
    {
      if ((! isxdigit(hex[i * 2])) || (! isxdigit(hex[i * 2 + 1])))
        return svn_error_create(SVN_ERR_BAD_CHECKSUM_PARSE, NULL, NULL);

      ((unsigned char *)(*checksum)->digest)[i] =
        (( isalpha(hex[i*2]) ? hex[i*2] - 'a' + 10 : hex[i*2] - '0') << 4) |
        ( isalpha(hex[i*2+1]) ? hex[i*2+1] - 'a' + 10 : hex[i*2+1] - '0');
      is_zeros |= (*checksum)->digest[i];
    }

  if (is_zeros == '\0')
    *checksum = NULL;

  return SVN_NO_ERROR;
}

svn_checksum_t *
svn_checksum_dup(const svn_checksum_t *checksum,
                 apr_pool_t *pool)
{
  /* The duplicate of a NULL checksum is a NULL... */
  if (checksum == NULL)
    return NULL;

  return svn_checksum__from_digest(checksum->digest, checksum->kind, pool);
}

svn_error_t *
svn_checksum(svn_checksum_t **checksum,
             svn_checksum_kind_t kind,
             const void *data,
             apr_size_t len,
             apr_pool_t *pool)
{
  apr_sha1_ctx_t sha1_ctx;

  SVN_ERR(validate_kind(kind));
  *checksum = svn_checksum_create(kind, pool);

  switch (kind)
    {
      case svn_checksum_md5:
        apr_md5((unsigned char *)(*checksum)->digest, data, len);
        break;

      case svn_checksum_sha1:
        apr_sha1_init(&sha1_ctx);
        apr_sha1_update(&sha1_ctx, data, len);
        apr_sha1_final((unsigned char *)(*checksum)->digest, &sha1_ctx);
        break;

      default:
        /* We really shouldn't get here, but if we do... */
        return svn_error_create(SVN_ERR_BAD_CHECKSUM_KIND, NULL, NULL);
    }

  return SVN_NO_ERROR;
}


svn_checksum_t *
svn_checksum_empty_checksum(svn_checksum_kind_t kind,
                            apr_pool_t *pool)
{
  const unsigned char *digest;

  switch (kind)
    {
      case svn_checksum_md5:
        digest = svn_md5__empty_string_digest();
        break;

      case svn_checksum_sha1:
        digest = svn_sha1__empty_string_digest();
        break;

      default:
        /* We really shouldn't get here, but if we do... */
        return NULL;
    }

  return svn_checksum__from_digest(digest, kind, pool);
}

struct svn_checksum_ctx_t
{
  void *apr_ctx;
  svn_checksum_kind_t kind;
};

svn_checksum_ctx_t *
svn_checksum_ctx_create(svn_checksum_kind_t kind,
                        apr_pool_t *pool)
{
  svn_checksum_ctx_t *ctx = apr_palloc(pool, sizeof(*ctx));

  ctx->kind = kind;
  switch (kind)
    {
      case svn_checksum_md5:
        ctx->apr_ctx = apr_palloc(pool, sizeof(apr_md5_ctx_t));
        apr_md5_init(ctx->apr_ctx);
        break;

      case svn_checksum_sha1:
        ctx->apr_ctx = apr_palloc(pool, sizeof(apr_sha1_ctx_t));
        apr_sha1_init(ctx->apr_ctx);
        break;

      default:
        return NULL;
    }

  return ctx;
}

svn_error_t *
svn_checksum_update(svn_checksum_ctx_t *ctx,
                    const void *data,
                    apr_size_t len)
{
  switch (ctx->kind)
    {
      case svn_checksum_md5:
        apr_md5_update(ctx->apr_ctx, data, len);
        break;

      case svn_checksum_sha1:
        apr_sha1_update(ctx->apr_ctx, data, len);
        break;

      default:
        /* We really shouldn't get here, but if we do... */
        return svn_error_create(SVN_ERR_BAD_CHECKSUM_KIND, NULL, NULL);
    }

  return SVN_NO_ERROR;
}

svn_error_t *
svn_checksum_final(svn_checksum_t **checksum,
                   const svn_checksum_ctx_t *ctx,
                   apr_pool_t *pool)
{
  *checksum = svn_checksum_create(ctx->kind, pool);

  switch (ctx->kind)
    {
      case svn_checksum_md5:
        apr_md5_final((unsigned char *)(*checksum)->digest, ctx->apr_ctx);
        break;

      case svn_checksum_sha1:
        apr_sha1_final((unsigned char *)(*checksum)->digest, ctx->apr_ctx);
        break;

      default:
        /* We really shouldn't get here, but if we do... */
        return svn_error_create(SVN_ERR_BAD_CHECKSUM_KIND, NULL, NULL);
    }

  return SVN_NO_ERROR;
}

apr_size_t
svn_checksum_size(const svn_checksum_t *checksum)
{
  return DIGESTSIZE(checksum->kind);
}