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/*
* Copyright (C) 2003-2013 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;
}
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