/*= -*- c-basic-offset: 4; indent-tabs-mode: nil; -*- * * librsync -- dynamic caching and delta update in HTTP * Id: tube.c,v 1.22 2001/03/18 10:51:05 mbp Exp * * Copyright (C) 2000, 2001 by Martin Pool * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU Lesser General Public License as published by * the Free Software Foundation; either version 2.1 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ /* | Where a calculator on the ENIAC is | equpped with 18,000 vaccuum tubes and | weighs 30 tons, computers in the | future may have only 1,000 vaccuum | tubes and perhaps weigh 1 1/2 | tons. | -- Popular Mechanics, March 1949 */ /* tube: a somewhat elastic but fairly small buffer for data passing * through a stream. * * In most cases the iter can adjust to send just as much data will * fit. In some cases that would be too complicated, because it has * to transmit an integer or something similar. So in that case we * stick whatever won't fit into a small buffer. * * A tube can contain some literal data to go out (typically command * bytes), and also an instruction to copy data from the stream's * input or from some other location. Both literal data and a copy * command can be queued at the same time, but only in that order and * at most one of each. */ /* * TODO: As an optimization, write it directly to the stream if * possible. But for simplicity don't do that yet. * * TODO: I think our current copy code will lock up if the application * only ever calls us with either input or output buffers, and not * both. So I guess in that case we might need to copy into some * temporary buffer space, and then back out again later. */ #include #include #include #include #include #include "rsync.h" #include "trace.h" #include "util.h" #include "job.h" #include "stream.h" static void rs_tube_catchup_write(rs_job_t *job) { rs_buffers_t *stream = job->stream; int len, remain; len = job->write_len; assert(len > 0); assert(len > 0); if ((size_t) len > stream->avail_out) len = stream->avail_out; if (!stream->avail_out) { rs_trace("no output space available"); return; } memcpy(stream->next_out, job->write_buf, len); stream->next_out += len; stream->avail_out -= len; remain = job->write_len - len; rs_trace("transmitted %d write bytes from tube, " "%d remain to be sent", len, remain); if (remain > 0) { /* Still something left in the tube... */ memmove(job->write_buf, job->write_buf + len, remain); } else { assert(remain == 0); } job->write_len = remain; } /** * Execute a copy command, taking data from the scoop. * * \sa rs_tube_catchup_copy() */ static void rs_tube_copy_from_scoop(rs_job_t *job) { size_t this_len; rs_buffers_t *stream = job->stream; this_len = job->copy_len; if (this_len > job->scoop_avail) { this_len = job->scoop_avail; } if (this_len > stream->avail_out) { this_len = stream->avail_out; } memcpy(stream->next_out, job->scoop_next, this_len); stream->next_out += this_len; stream->avail_out -= this_len; job->scoop_avail -= this_len; job->scoop_next += this_len; job->copy_len -= this_len; rs_trace("caught up on %ld copied bytes from scoop, %ld remain there, " "%ld remain to be copied", (long) this_len, (long) job->scoop_avail, (long) job->copy_len); } /** * Catch up on an outstanding copy command. * * Takes data from the scoop, and the input (in that order), and * writes as much as will fit to the output, up to the limit of the * outstanding copy. */ static void rs_tube_catchup_copy(rs_job_t *job) { rs_buffers_t *stream = job->stream; assert(job->write_len == 0); assert(job->copy_len > 0); if (job->scoop_avail && job->copy_len) { /* there's still some data in the scoop, so we should use that. */ rs_tube_copy_from_scoop(job); } if (job->copy_len) { size_t this_copy; this_copy = rs_buffers_copy(stream, job->copy_len); job->copy_len -= this_copy; rs_trace("copied %.0f bytes from input buffer, %.0f remain to be copied", (double) this_copy, (double) job->copy_len); } } /* * Put whatever will fit from the tube into the output of the stream. * Return RS_DONE if the tube is now empty and ready to accept another * command, RS_BLOCKED if there is still stuff waiting to go out. */ int rs_tube_catchup(rs_job_t *job) { if (job->write_len) rs_tube_catchup_write(job); if (job->write_len) { /* there is still write data queued, so we can't send * anything else. */ return RS_BLOCKED; } if (job->copy_len) rs_tube_catchup_copy(job); if (job->copy_len) { if (job->stream->eof_in && !job->stream->avail_in && !job->scoop_avail) { rs_log(RS_LOG_ERR, "reached end of file while copying literal data through buffers"); return RS_INPUT_ENDED; } return RS_BLOCKED; } return RS_DONE; } /* Check whether there is data in the tube waiting to go out. So if true * this basically means that the previous command has finished doing all its * output. */ int rs_tube_is_idle(rs_job_t const *job) { return job->write_len == 0 && job->copy_len == 0; } /** * Queue up a request to copy through \p len bytes from the input to * the output of the stream. * * The data is copied from the scoop (if there is anything there) or * from the input, on the next call to rs_tube_write(). * * We can only accept this request if there is no copy command already * pending. */ /* TODO: Try to do the copy immediately, and return a result. Then, * people can try to continue if possible. Is this really required? * Callers can just go out and back in again after flushing the * tube. */ void rs_tube_copy(rs_job_t *job, int len) { assert(job->copy_len == 0); job->copy_len = len; } /* * Push some data into the tube for storage. The tube's never * supposed to get very big, so this will just pop loudly if you do * that. * * We can't accept write data if there's already a copy command in the * tube, because the write data comes out first. */ void rs_tube_write(rs_job_t *job, const void *buf, size_t len) { assert(job->copy_len == 0); if (len > sizeof(job->write_buf) - job->write_len) { rs_fatal("tube popped when trying to write %ld bytes!", (long) len); } memcpy(job->write_buf + job->write_len, buf, len); job->write_len += len; }