Re: [FFmpeg-devel] [PATCH v2 2/6] avformat: add Android content resolver protocol support

[Matthieu Bouron <matthieu.bouron@gmail.com>]

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On Tue, Feb 27, 2024 at 03:50:38PM +0100, Matthieu Bouron wrote:
> Handles Android content-uri starting with content://.
> ---

[...]

New patch attached (I moved an unrelated chunk to the previous commit).

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From 6ef059b721c1b1635565cc9e7d836be4733c928d Mon Sep 17 00:00:00 2001
From: Matthieu Bouron <matthieu.bouron@gmail.com>
Date: Mon, 12 Feb 2024 23:14:35 +0100
Subject: [PATCH v3 2/6] avformat: add Android content resolver protocol
 support

Handles Android content-uri starting with content://.
---
 configure               |   2 +
 doc/APIchanges          |   3 +
 libavcodec/jni.c        |   1 +
 libavformat/Makefile    |   1 +
 libavformat/file.c      | 157 ++++++++++++++++++++++++++++++++++++++++
 libavformat/protocols.c |   1 +
 6 files changed, 165 insertions(+)

diff --git a/configure b/configure
index bb5e630bad..790a1df7c8 100755
--- a/configure
+++ b/configure
@@ -3655,6 +3655,8 @@ xcbgrab_indev_suggest="libxcb_shm libxcb_shape libxcb_xfixes"
 xv_outdev_deps="xlib_xv xlib_x11 xlib_xext"
 
 # protocols
+android_content_protocol_deps="jni"
+android_content_protocol_select="file_protocol"
 async_protocol_deps="threads"
 bluray_protocol_deps="libbluray"
 ffrtmpcrypt_protocol_conflict="librtmp_protocol"
diff --git a/doc/APIchanges b/doc/APIchanges
index 10f6667e9e..258e953ca6 100644
--- a/doc/APIchanges
+++ b/doc/APIchanges
@@ -2,6 +2,9 @@ The last version increases of all libraries were on 2023-02-09
 
 API changes, most recent first:
 
+2024-02-xx - xxxxxxxxxx - lavc 60.41.100 - jni.h
+  Add av_jni_set_android_app_ctx() and av_jni_get_android_app_ctx().
+
 2024-02-26 - xxxxxxxxxx - lavf 60.22.101 - avformat.h
   AV_DISPOSITION_DEPENDENT may now also be used for video streams
   intended to be merged with other video streams for presentation.
diff --git a/libavcodec/jni.c b/libavcodec/jni.c
index cfe95bd1ec..1193c608c3 100644
--- a/libavcodec/jni.c
+++ b/libavcodec/jni.c
@@ -35,6 +35,7 @@
 #include "ffjni.h"
 
 static void *java_vm;
+static void *android_app_ctx;
 static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
 
 int av_jni_set_java_vm(void *vm, void *log_ctx)
diff --git a/libavformat/Makefile b/libavformat/Makefile
index 4a380668bd..08fe98a535 100644
--- a/libavformat/Makefile
+++ b/libavformat/Makefile
@@ -657,6 +657,7 @@ OBJS-$(CONFIG_LIBOPENMPT_DEMUXER)        += libopenmpt.o
 OBJS-$(CONFIG_VAPOURSYNTH_DEMUXER)       += vapoursynth.o
 
 # protocols I/O
+OBJS-$(CONFIG_ANDROID_CONTENT_PROTOCOL)  += file.o
 OBJS-$(CONFIG_ASYNC_PROTOCOL)            += async.o
 OBJS-$(CONFIG_APPLEHTTP_PROTOCOL)        += hlsproto.o
 OBJS-$(CONFIG_BLURAY_PROTOCOL)           += bluray.o
diff --git a/libavformat/file.c b/libavformat/file.c
index 64df7ff6fb..1b2b69f090 100644
--- a/libavformat/file.c
+++ b/libavformat/file.c
@@ -40,6 +40,12 @@
 #include <stdlib.h>
 #include "os_support.h"
 #include "url.h"
+#if CONFIG_ANDROID_CONTENT_PROTOCOL
+#include <jni.h>
+#include "libavcodec/jni.h"
+#include "libavcodec/ffjni.c"
+#endif
+
 
 /* Some systems may not have S_ISFIFO */
 #ifndef S_ISFIFO
@@ -101,6 +107,21 @@ typedef struct FileContext {
     int64_t initial_pos;
 } FileContext;
 
+
+#if CONFIG_ANDROID_CONTENT_PROTOCOL
+static const AVOption android_content_options[] = {
+    { "blocksize", "set I/O operation maximum block size", offsetof(FileContext, blocksize), AV_OPT_TYPE_INT, { .i64 = INT_MAX }, 1, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM },
+    { NULL }
+};
+
+static const AVClass android_content_class = {
+    .class_name = "android_content",
+    .item_name  = av_default_item_name,
+    .option     = android_content_options,
+    .version    = LIBAVUTIL_VERSION_INT,
+};
+#endif
+
 static const AVOption file_options[] = {
     { "truncate", "truncate existing files on write", offsetof(FileContext, trunc), AV_OPT_TYPE_BOOL, { .i64 = 1 }, 0, 1, AV_OPT_FLAG_ENCODING_PARAM },
     { "blocksize", "set I/O operation maximum block size", offsetof(FileContext, blocksize), AV_OPT_TYPE_INT, { .i64 = INT_MAX }, 1, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM },
@@ -524,3 +545,139 @@ const URLProtocol ff_fd_protocol = {
 };
 
 #endif /* CONFIG_FD_PROTOCOL */
+
+#if CONFIG_ANDROID_CONTENT_PROTOCOL
+
+struct JFields {
+    jclass uri_class;
+    jmethodID parse_id;
+
+    jclass context_class;
+    jmethodID get_content_resolver_id;
+
+    jclass content_resolver_class;
+    jmethodID open_file_descriptor_id;
+
+    jclass parcel_file_descriptor_class;
+    jmethodID detach_fd_id;
+};
+
+#define OFFSET(x) offsetof(struct JFields, x)
+static const struct FFJniField jfields_mapping[] = {
+    { "android/net/Uri", NULL, NULL, FF_JNI_CLASS, OFFSET(uri_class), 1 },
+        { "android/net/Uri", "parse", "(Ljava/lang/String;)Landroid/net/Uri;", FF_JNI_STATIC_METHOD, OFFSET(parse_id), 1 },
+
+    { "android/content/Context", NULL, NULL, FF_JNI_CLASS, OFFSET(context_class), 1 },
+        { "android/content/Context", "getContentResolver", "()Landroid/content/ContentResolver;", FF_JNI_METHOD, OFFSET(get_content_resolver_id), 1 },
+
+    { "android/content/ContentResolver", NULL, NULL, FF_JNI_CLASS, OFFSET(content_resolver_class), 1 },
+        { "android/content/ContentResolver", "openFileDescriptor", "(Landroid/net/Uri;Ljava/lang/String;)Landroid/os/ParcelFileDescriptor;", FF_JNI_METHOD, OFFSET(open_file_descriptor_id), 1 },
+
+    { "android/os/ParcelFileDescriptor", NULL, NULL, FF_JNI_CLASS, OFFSET(parcel_file_descriptor_class), 1 },
+        { "android/os/ParcelFileDescriptor", "detachFd", "()I", FF_JNI_METHOD, OFFSET(detach_fd_id), 1 },
+
+    { NULL }
+};
+#undef OFFSET
+
+static int android_content_open(URLContext *h, const char *filename, int flags)
+{
+    FileContext *c = h->priv_data;
+    int fd, ret;
+    const char *mode_str = "r";
+
+    JNIEnv *env;
+    struct JFields jfields = { 0 };
+    jobject application_context = NULL;
+    jobject url = NULL;
+    jobject mode = NULL;
+    jobject uri = NULL;
+    jobject content_resolver = NULL;
+    jobject parcel_file_descriptor = NULL;
+
+    env = ff_jni_get_env(c);
+    if (!env) {
+        return AVERROR(EINVAL);
+    }
+
+    ret = ff_jni_init_jfields(env, &jfields, jfields_mapping, 0, c);
+    if (ret < 0) {
+        av_log(c, AV_LOG_ERROR, "failed to initialize jni fields\n");
+        return ret;
+    }
+
+    application_context = av_jni_get_android_app_ctx();
+    if (!application_context) {
+        av_log(c, AV_LOG_ERROR, "application context is not set\n");
+        ret = AVERROR_EXTERNAL;
+        goto done;
+    }
+
+    url = ff_jni_utf_chars_to_jstring(env, filename, c);
+    if (!url) {
+        ret = AVERROR_EXTERNAL;
+        goto done;
+    }
+
+    if (flags & AVIO_FLAG_WRITE && flags & AVIO_FLAG_READ)
+        mode_str = "rw";
+    else if (flags & AVIO_FLAG_WRITE)
+        mode_str = "w";
+
+    mode = ff_jni_utf_chars_to_jstring(env, mode_str, c);
+    if (!mode) {
+        ret = AVERROR_EXTERNAL;
+        goto done;
+    }
+
+    uri = (*env)->CallStaticObjectMethod(env, jfields.uri_class, jfields.parse_id, url);
+    ret = ff_jni_exception_check(env, 1, c);
+    if (ret < 0)
+        goto done;
+
+    content_resolver = (*env)->CallObjectMethod(env, application_context, jfields.get_content_resolver_id);
+    ret = ff_jni_exception_check(env, 1, c);
+    if (ret < 0)
+        goto done;
+
+    parcel_file_descriptor = (*env)->CallObjectMethod(env, content_resolver, jfields.open_file_descriptor_id, uri, mode);
+    ret = ff_jni_exception_check(env, 1, c);
+    if (ret < 0)
+        goto done;
+
+    fd = (*env)->CallIntMethod(env, parcel_file_descriptor, jfields.detach_fd_id);
+    ret = ff_jni_exception_check(env, 1, c);
+    if (ret < 0)
+        goto done;
+
+#if HAVE_SETMODE
+    setmode(fd, O_BINARY);
+#endif
+    c->fd = fd;
+    h->is_streamed = 0;
+
+done:
+    (*env)->DeleteLocalRef(env, url);
+    (*env)->DeleteLocalRef(env, mode);
+    (*env)->DeleteLocalRef(env, uri);
+    (*env)->DeleteLocalRef(env, content_resolver);
+    (*env)->DeleteLocalRef(env, parcel_file_descriptor);
+    ff_jni_reset_jfields(env, &jfields, jfields_mapping, 0, c);
+
+    return ret;
+}
+
+URLProtocol ff_android_content_protocol = {
+    .name                = "content",
+    .url_open            = android_content_open,
+    .url_read            = file_read,
+    .url_write           = file_write,
+    .url_seek            = file_seek,
+    .url_close           = file_close,
+    .url_get_file_handle = file_get_handle,
+    .url_check           = NULL,
+    .priv_data_size      = sizeof(FileContext),
+    .priv_data_class     = &android_content_class,
+};
+
+#endif /* CONFIG_ANDROID_CONTENT_PROTOCOL */
diff --git a/libavformat/protocols.c b/libavformat/protocols.c
index 360018b17c..93a6d67261 100644
--- a/libavformat/protocols.c
+++ b/libavformat/protocols.c
@@ -24,6 +24,7 @@
 
 #include "url.h"
 
+extern const URLProtocol ff_android_content_protocol;
 extern const URLProtocol ff_async_protocol;
 extern const URLProtocol ff_bluray_protocol;
 extern const URLProtocol ff_cache_protocol;
-- 
2.44.0


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