src/lib-mail/istream-qp-encoder.c

/* Copyright (c) 2017-2018 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "buffer.h"
#include "hex-binary.h"
#include "qp-encoder.h"
#include "istream-private.h"
#include "istream-qp.h"

struct qp_encoder_istream {
    struct istream_private istream;
    buffer_t *buf;
    struct qp_encoder *qp;
};

static void i_stream_qp_encoder_close(struct iostream_private *stream,
                      bool close_parent)
{
    struct qp_encoder_istream *bstream =
        (struct qp_encoder_istream *)stream;

    if (bstream->qp != NULL)
        qp_encoder_deinit(&bstream->qp);
    buffer_free(&bstream->buf);
    if (close_parent)
        i_stream_close(bstream->istream.parent);
}

static ssize_t i_stream_qp_encoder_read(struct istream_private *stream)
{
    struct qp_encoder_istream *bstream =
        (struct qp_encoder_istream *)stream;
    const unsigned char *data;
    size_t size;
    int ret;

    for(;;) {
        if (stream->skip > 0) {
            i_assert(stream->skip <= bstream->buf->used);
            buffer_delete(bstream->buf, 0, stream->skip);
            stream->pos -= stream->skip;
            stream->skip = 0;
        }

        stream->buffer = bstream->buf->data;
        i_assert(stream->pos <= bstream->buf->used);

        if (stream->pos >= bstream->istream.max_buffer_size) {
            /* stream buffer still at maximum */
            return -2;
        }

        /* if something is already interpolated, return as much of it as
           we can */
        if (bstream->buf->used > 0) {
            size_t new_pos, bytes;

            /* only return up to max_buffer_size bytes, even when buffer
               actually has more, as not to confuse the caller */
            if (bstream->buf->used <= bstream->istream.max_buffer_size) {
                new_pos = bstream->buf->used;
                if (stream->parent->eof)
                    stream->istream.eof = TRUE;
            } else {
                new_pos = bstream->istream.max_buffer_size;
            }

            bytes = new_pos - stream->pos;
            stream->pos = new_pos;
            return (ssize_t)bytes;
        }

        /* need to read more input */
        ret = i_stream_read_more_memarea(stream->parent, &data, &size);
        if (ret == 0)
            return ret;
        if (size == 0 && ret == -1) {
            stream->istream.stream_errno =
                stream->parent->stream_errno;
            stream->istream.eof = stream->parent->eof;
            return ret;
        }
        qp_encoder_more(bstream->qp, data, size);
        i_stream_skip(stream->parent, size);
    }
}

static void
i_stream_qp_encoder_seek(struct istream_private *stream,
                 uoff_t v_offset, bool mark)
{
    struct qp_encoder_istream *bstream =
        (struct qp_encoder_istream *)stream;

    if (v_offset < stream->istream.v_offset) {
        /* seeking backwards - go back to beginning and seek
           forward from there. */
        stream->parent_expected_offset = stream->parent_start_offset;
        stream->skip = stream->pos = 0;
        stream->istream.v_offset = 0;
        i_stream_seek(stream->parent, 0);
        qp_encoder_finish(bstream->qp);
        buffer_set_used_size(bstream->buf, 0);
    }
    i_stream_default_seek_nonseekable(stream, v_offset, mark);
}

struct istream *i_stream_create_qp_encoder(struct istream *input,
                       enum qp_encoder_flag flags)
{
    struct qp_encoder_istream *bstream;

    bstream = i_new(struct qp_encoder_istream, 1);
    bstream->istream.max_buffer_size = input->real_stream->max_buffer_size;
    bstream->buf = buffer_create_dynamic(default_pool, 128);
    bstream->qp = qp_encoder_init(bstream->buf, ISTREAM_QP_ENCODER_MAX_LINE_LENGTH, flags);

    bstream->istream.iostream.close = i_stream_qp_encoder_close;
    bstream->istream.read = i_stream_qp_encoder_read;
    bstream->istream.seek = i_stream_qp_encoder_seek;

    bstream->istream.istream.readable_fd = FALSE;
    bstream->istream.istream.blocking = input->blocking;
    bstream->istream.istream.seekable = input->seekable;
    return i_stream_create(&bstream->istream, input,
                   i_stream_get_fd(input), 0);
}