stream: add a file cache

For remarks, pretty much see the manpage additions. Could help with
network streams that require too much seeking (maybe), or might be
extended to help with the use case of watching and downloading a file
at the same time.

In general, it might be a useless feature and could be removed again.

1 files changed, 149 insertions, 0 deletions

diff --git a/stream/cache_file.c b/stream/cache_file.c
new file mode 100644
index 0000000000..dfdd8390dc
--- /dev/null
+++ b/stream/cache_file.c
@@ -0,0 +1,149 @@
+/*
+ * This file is part of mpv.
+ *
+ * mpv 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.
+ *
+ * mpv 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 mpv.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include <stdio.h>
+#include <stdint.h>
+
+#include "common/common.h"
+#include "common/msg.h"
+
+#include "options/options.h"
+
+#include "stream.h"
+
+#define BLOCK_SIZE 1024LL
+#define BLOCK_ALIGN(p) ((p) & ~(BLOCK_SIZE - 1))
+
+struct priv {
+    struct stream *original;
+    FILE *cache_file;
+    uint8_t *block_bits;    // 1 bit for each BLOCK_SIZE, whether block was read
+    int64_t size;           // currently known size
+    int64_t max_size;       // max. size for block_bits and cache_file
+};
+
+static bool test_bit(struct priv *p, int64_t pos)
+{
+    if (pos < 0 || pos >= p->size)
+        return false;
+    size_t block = pos / BLOCK_SIZE;
+    return p->block_bits[block / 8] & (1 << (block % 8));
+}
+
+static void set_bit(struct priv *p, int64_t pos, bool bit)
+{
+    if (pos < 0 || pos >= p->size)
+        return;
+    size_t block = pos / BLOCK_SIZE;
+    unsigned int m = (1 << (block % 8));
+    p->block_bits[block / 8] = (p->block_bits[block / 8] & ~m) | (bit ? m : 0);
+}
+
+static int fill_buffer(stream_t *s, char *buffer, int max_len)
+{
+    struct priv *p = s->priv;
+    if (s->pos < 0)
+        return -1;
+    if (s->pos >= p->max_size) {
+        if (stream_seek(p->original, s->pos) < 1)
+            return -1;
+        return stream_read(p->original, buffer, max_len);
+    }
+    // Size of file changes -> invalidate last block
+    if (s->pos >= p->size - BLOCK_SIZE) {
+        int64_t new_size = -1;
+        stream_control(s, STREAM_CTRL_GET_SIZE, &new_size);
+        if (new_size != p->size)
+            set_bit(p, BLOCK_ALIGN(p->size), 0);
+        p->size = MPMIN(p->max_size, new_size);
+    }
+    int64_t aligned = BLOCK_ALIGN(s->pos);
+    if (!test_bit(p, aligned)) {
+        char tmp[BLOCK_SIZE];
+        stream_seek(p->original, aligned);
+        int r = stream_read(p->original, tmp, BLOCK_SIZE);
+        if (r < BLOCK_SIZE) {
+            if (p->size < 0) {
+                MP_WARN(s, "suspected EOF\n");
+            } else if (aligned + r < p->size) {
+                MP_ERR(s, "unexpected EOF\n");
+                return -1;
+            }
+        }
+        if (fseeko(p->cache_file, aligned, SEEK_SET))
+            return -1;
+        if (fwrite(tmp, r, 1, p->cache_file) != 1)
+            return -1;
+        set_bit(p, aligned, 1);
+    }
+    if (fseeko(p->cache_file, s->pos, SEEK_SET))
+        return -1;
+    // align/limit to blocks
+    max_len = MPMIN(max_len, BLOCK_SIZE - (s->pos % BLOCK_SIZE));
+    // Limit to max. known file size
+    max_len = MPMIN(max_len, p->size - s->pos);
+    return fread(buffer, 1, max_len, p->cache_file);
+}
+
+static int seek(stream_t *s, int64_t newpos)
+{
+    return 1;
+}
+
+static int control(stream_t *s, int cmd, void *arg)
+{
+    struct priv *p = s->priv;
+    return stream_control(p->original, cmd, arg);
+}
+
+static void s_close(stream_t *s)
+{
+    struct priv *p = s->priv;
+    if (p->cache_file)
+        fclose(p->cache_file);
+    talloc_free(p);
+}
+
+// return 1 on success, 0 if disabled, -1 on error
+int stream_file_cache_init(stream_t *cache, stream_t *stream,
+                           struct mp_cache_opts *opts)
+{
+    if (!opts->file || !opts->file[0] || opts->file_max < 1)
+        return 0;
+
+    FILE *file = fopen(opts->file, "wb+");
+    if (!file) {
+        MP_ERR(cache, "can't open cache file '%s'\n", opts->file);
+        return -1;
+    }
+
+    struct priv *p = talloc_zero(NULL, struct priv);
+
+    cache->priv = p;
+    p->original = stream;
+    p->cache_file = file;
+    p->max_size = opts->file_max * 1024LL;
+
+    // file_max can be INT_MAX, so this is at most about 256MB
+    p->block_bits = talloc_zero_size(p, (p->max_size / BLOCK_SIZE + 1) / 8 + 1);
+
+    cache->seek = seek;
+    cache->fill_buffer = fill_buffer;
+    cache->control = control;
+    cache->close = s_close;
+
+    return 1;
+}