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-rw-r--r--src/input/plugins/RewindInputPlugin.cxx251
1 files changed, 251 insertions, 0 deletions
diff --git a/src/input/plugins/RewindInputPlugin.cxx b/src/input/plugins/RewindInputPlugin.cxx
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+++ b/src/input/plugins/RewindInputPlugin.cxx
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+/*
+ * Copyright (C) 2003-2014 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 "RewindInputPlugin.hxx"
+#include "../InputStream.hxx"
+#include "../InputPlugin.hxx"
+
+#include <assert.h>
+#include <string.h>
+#include <stdio.h>
+
+extern const InputPlugin rewind_input_plugin;
+
+struct RewindInputStream {
+ InputStream base;
+
+ InputStream *input;
+
+ /**
+ * The read position within the buffer. Undefined as long as
+ * ReadingFromBuffer() 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];
+
+ RewindInputStream(InputStream *_input)
+ :base(rewind_input_plugin, _input->uri.c_str(),
+ _input->mutex, _input->cond),
+ input(_input), tail(0) {
+ }
+
+ ~RewindInputStream() {
+ input->Close();
+ }
+
+ /**
+ * Are we currently reading from the buffer, and does the
+ * buffer contain more data for the next read operation?
+ */
+ bool ReadingFromBuffer() const {
+ return tail > 0 && base.offset < 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.
+ */
+ void CopyAttributes() {
+ InputStream *dest = &base;
+ const InputStream *src = input;
+
+ assert(dest != src);
+
+ bool dest_ready = dest->ready;
+
+ dest->ready = src->ready;
+ dest->seekable = src->seekable;
+ dest->size = src->size;
+ dest->offset = src->offset;
+
+ if (!dest_ready && src->ready)
+ dest->mime = src->mime;
+ }
+};
+
+static void
+input_rewind_close(InputStream *is)
+{
+ RewindInputStream *r = (RewindInputStream *)is;
+
+ delete r;
+}
+
+static bool
+input_rewind_check(InputStream *is, Error &error)
+{
+ RewindInputStream *r = (RewindInputStream *)is;
+
+ return r->input->Check(error);
+}
+
+static void
+input_rewind_update(InputStream *is)
+{
+ RewindInputStream *r = (RewindInputStream *)is;
+
+ if (!r->ReadingFromBuffer())
+ r->CopyAttributes();
+}
+
+static Tag *
+input_rewind_tag(InputStream *is)
+{
+ RewindInputStream *r = (RewindInputStream *)is;
+
+ return r->input->ReadTag();
+}
+
+static bool
+input_rewind_available(InputStream *is)
+{
+ RewindInputStream *r = (RewindInputStream *)is;
+
+ return r->input->IsAvailable();
+}
+
+static size_t
+input_rewind_read(InputStream *is, void *ptr, size_t size,
+ Error &error)
+{
+ RewindInputStream *r = (RewindInputStream *)is;
+
+ if (r->ReadingFromBuffer()) {
+ /* 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 = r->input->Read(ptr, size, error);
+
+ if (r->input->offset > (InputPlugin::offset_type)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);
+ }
+
+ r->CopyAttributes();
+
+ return nbytes;
+ }
+}
+
+static bool
+input_rewind_eof(InputStream *is)
+{
+ RewindInputStream *r = (RewindInputStream *)is;
+
+ return !r->ReadingFromBuffer() && r->input->IsEOF();
+}
+
+static bool
+input_rewind_seek(InputStream *is, InputPlugin::offset_type offset,
+ int whence,
+ Error &error)
+{
+ RewindInputStream *r = (RewindInputStream *)is;
+
+ assert(is->ready);
+
+ if (whence == SEEK_SET && r->tail > 0 &&
+ offset <= (InputPlugin::offset_type)r->tail) {
+ /* buffered seek */
+
+ assert(!r->ReadingFromBuffer() ||
+ 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 = r->input->Seek(offset, whence, error);
+ r->CopyAttributes();
+
+ /* disable the buffer, because r->input has left the
+ buffered range now */
+ r->tail = 0;
+
+ return success;
+ }
+}
+
+const InputPlugin rewind_input_plugin = {
+ nullptr,
+ nullptr,
+ nullptr,
+ nullptr,
+ input_rewind_close,
+ input_rewind_check,
+ input_rewind_update,
+ input_rewind_tag,
+ input_rewind_available,
+ input_rewind_read,
+ input_rewind_eof,
+ input_rewind_seek,
+};
+
+InputStream *
+input_rewind_open(InputStream *is)
+{
+ assert(is != nullptr);
+ assert(is->offset == 0);
+
+ if (is->seekable)
+ /* seekable resources don't need this plugin */
+ return is;
+
+ RewindInputStream *c = new RewindInputStream(is);
+ return &c->base;
+}