src/lib/istream-hash.c

/* Copyright (c) 2013-2018 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "hash-method.h"
#include "istream-private.h"
#include "istream-hash.h"

struct hash_istream {
    struct istream_private istream;

    const struct hash_method *method;
    void *hash_context;
    uoff_t high_offset;
};

static ssize_t
i_stream_hash_read(struct istream_private *stream)
{
    struct hash_istream *hstream = (struct hash_istream *)stream;
    const unsigned char *data;
    size_t size;
    uoff_t skip;
    ssize_t ret;

    i_stream_seek(stream->parent, stream->parent_start_offset +
              stream->istream.v_offset);

    ret = i_stream_read_copy_from_parent(&stream->istream);
    if (ret > 0 && hstream->hash_context != NULL) {
        data = i_stream_get_data(&stream->istream, &size);
        i_assert((size_t)ret <= size);

        i_assert(stream->istream.v_offset <= hstream->high_offset);
        skip = hstream->high_offset - stream->istream.v_offset;
        if (skip < (size_t)size) {
            hstream->high_offset += (size-skip);
            hstream->method->loop(hstream->hash_context,
                          data+skip, size-skip);
        }
    } else if (ret < 0) {
        /* we finished hashing it. don't access it anymore, because
           the memory pointed by the hash may be freed before the
           istream itself */
        hstream->hash_context = NULL;
    }
    return ret;
}

static void
i_stream_hash_seek(struct istream_private *stream,
           uoff_t v_offset, bool mark ATTR_UNUSED)
{
    struct hash_istream *hstream = (struct hash_istream *)stream;

    if (hstream->hash_context != NULL) {
        io_stream_set_error(&stream->iostream,
            "Seeking not supported before hashing is finished");
        stream->istream.stream_errno = ESPIPE;
    }
    stream->istream.v_offset = v_offset;
    stream->skip = stream->pos = 0;
}

struct istream *
i_stream_create_hash(struct istream *input, const struct hash_method *method,
             void *hash_context)
{
    struct hash_istream *hstream;

    hstream = i_new(struct hash_istream, 1);
    hstream->istream.max_buffer_size = input->real_stream->max_buffer_size;
    hstream->istream.stream_size_passthrough = TRUE;

    hstream->istream.read = i_stream_hash_read;
    hstream->istream.seek = i_stream_hash_seek;

    hstream->istream.istream.readable_fd = input->readable_fd;
    hstream->istream.istream.blocking = input->blocking;
    hstream->istream.istream.seekable = input->seekable;

    hstream->method = method;
    hstream->hash_context = hash_context;
    return i_stream_create(&hstream->istream, input,
                   i_stream_get_fd(input), 0);
}