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-rw-r--r--src/input/rewind_input_plugin.c238
1 files changed, 238 insertions, 0 deletions
diff --git a/src/input/rewind_input_plugin.c b/src/input/rewind_input_plugin.c
new file mode 100644
index 000000000..0a874a29c
--- /dev/null
+++ b/src/input/rewind_input_plugin.c
@@ -0,0 +1,238 @@
+/*
+ * Copyright (C) 2003-2009 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "config.h"
+#include "input/rewind_input_plugin.h"
+#include "input/curl_input_plugin.h"
+#include "input_plugin.h"
+#include "tag.h"
+
+#include <glib.h>
+
+#include <assert.h>
+#include <stdio.h>
+
+#undef G_LOG_DOMAIN
+#define G_LOG_DOMAIN "input_rewind"
+
+struct input_rewind {
+ struct input_stream input;
+
+ /**
+ * The read position within the buffer. Undefined as long as
+ * reading_from_buffer() returns false.
+ */
+ size_t head;
+
+ /**
+ * The write/append position within the buffer.
+ */
+ size_t tail;
+
+ /**
+ * The size of this buffer is the maximum number of bytes
+ * which can be rewinded cheaply without passing the "seek"
+ * call to CURL.
+ *
+ * The origin of this buffer is always the beginning of the
+ * stream (offset 0).
+ */
+ char buffer[64 * 1024];
+};
+
+/**
+ * Are we currently reading from the buffer, and does the buffer
+ * contain more data for the next read operation?
+ */
+static bool
+reading_from_buffer(const struct input_stream *is)
+{
+ const struct input_rewind *r = is->data;
+
+ return r->tail > 0 && is->offset < r->input.offset;
+}
+
+/**
+ * Copy public attributes from the underlying input stream to the
+ * "rewind" input stream. This function is called when a method of
+ * the underlying stream has returned, which may have modified these
+ * attributes.
+ */
+static void
+copy_attributes(struct input_stream *dest)
+{
+ const struct input_rewind *r = dest->data;
+ const struct input_stream *src = &r->input;
+
+ dest->ready = src->ready;
+ dest->seekable = src->seekable;
+ dest->error = src->error;
+ dest->size = src->size;
+ dest->offset = src->offset;
+
+ if (dest->mime == NULL && src->mime != NULL)
+ /* this is set only once, and the duplicated pointer
+ is freed by input_stream_close() */
+ dest->mime = g_strdup(src->mime);
+}
+
+static void
+input_rewind_close(struct input_stream *is)
+{
+ struct input_rewind *r = is->data;
+
+ input_stream_close(&r->input);
+
+ g_free(r);
+}
+
+static struct tag *
+input_rewind_tag(struct input_stream *is)
+{
+ struct input_rewind *r = is->data;
+
+ return input_stream_tag(&r->input);
+}
+
+static int
+input_rewind_buffer(struct input_stream *is)
+{
+ struct input_rewind *r = is->data;
+
+ int ret = input_stream_buffer(&r->input);
+ if (ret < 0 || !reading_from_buffer(is))
+ copy_attributes(is);
+
+ return ret;
+}
+
+static size_t
+input_rewind_read(struct input_stream *is, void *ptr, size_t size)
+{
+ struct input_rewind *r = is->data;
+
+ if (reading_from_buffer(is)) {
+ /* buffered read */
+
+ assert(r->head == (size_t)is->offset);
+ assert(r->tail == (size_t)r->input.offset);
+
+ if (size > r->tail - r->head)
+ size = r->tail - r->head;
+
+ memcpy(ptr, r->buffer + r->head, size);
+ r->head += size;
+ is->offset += size;
+
+ return size;
+ } else {
+ /* pass method call to underlying stream */
+
+ size_t nbytes = input_stream_read(&r->input, ptr, size);
+
+ if (r->input.offset > (off_t)sizeof(r->buffer))
+ /* disable buffering */
+ r->tail = 0;
+ else if (r->tail == (size_t)is->offset) {
+ /* append to buffer */
+
+ memcpy(r->buffer + r->tail, ptr, nbytes);
+ r->tail += nbytes;
+
+ assert(r->tail == (size_t)r->input.offset);
+ }
+
+ copy_attributes(is);
+
+ return nbytes;
+ }
+}
+
+static bool
+input_rewind_eof(G_GNUC_UNUSED struct input_stream *is)
+{
+ struct input_rewind *r = is->data;
+
+ return !reading_from_buffer(is) && input_stream_eof(&r->input);
+}
+
+static bool
+input_rewind_seek(struct input_stream *is, off_t offset, int whence)
+{
+ struct input_rewind *r = is->data;
+
+ assert(is->ready);
+
+ if (whence == SEEK_SET && r->tail > 0 && offset <= (off_t)r->tail) {
+ /* buffered seek */
+
+ assert(!reading_from_buffer(is) ||
+ r->head == (size_t)is->offset);
+ assert(r->tail == (size_t)r->input.offset);
+
+ r->head = (size_t)offset;
+ is->offset = offset;
+
+ return true;
+ } else {
+ bool success = input_stream_seek(&r->input, offset, whence);
+ copy_attributes(is);
+
+ /* disable the buffer, because r->input has left the
+ buffered range now */
+ r->tail = 0;
+
+ return success;
+ }
+}
+
+static const struct input_plugin rewind_input_plugin = {
+ .close = input_rewind_close,
+ .tag = input_rewind_tag,
+ .buffer = input_rewind_buffer,
+ .read = input_rewind_read,
+ .eof = input_rewind_eof,
+ .seek = input_rewind_seek,
+};
+
+void
+input_rewind_open(struct input_stream *is)
+{
+ struct input_rewind *c;
+
+ assert(is != NULL);
+ assert(is->offset == 0);
+
+ if (is->plugin != &input_plugin_curl)
+ /* due to limitations in the input_plugin API, we only
+ (explicitly) support the CURL input plugin */
+ return;
+
+ c = g_new(struct input_rewind, 1);
+ c->tail = 0;
+
+ /* move the CURL input stream to c->input */
+ c->input = *is;
+ input_curl_reinit(&c->input);
+
+ /* convert the existing input_stream pointer to a "rewind"
+ input stream */
+ is->plugin = &rewind_input_plugin;
+ is->data = c;
+}