Camera: Add methods for read-only access to metadata.

- Define a read-only version of camera_metadata_entry_t
- Support finding with read-only output
- Add const to clone method input camera_metadata_t.

Bug: 6243944
Change-Id: Icd581e48f5fafaa6da22ca25e872bf3ede192222

2 files changed, 45 insertions, 6 deletions

diff --git a/camera/include/system/camera_metadata.h b/camera/include/system/camera_metadata.h
index f44338db..3396312e 100644
--- a/camera/include/system/camera_metadata.h
+++ b/camera/include/system/camera_metadata.h
@@ -14,8 +14,8 @@
  * limitations under the License.
  */
 
-#ifndef SYSTEM_CORE_INCLUDE_ANDROID_CAMERA_METADATA_H
-#define SYSTEM_CORE_INCLUDE_ANDROID_CAMERA_METADATA_H
+#ifndef SYSTEM_MEDIA_INCLUDE_ANDROID_CAMERA_METADATA_H
+#define SYSTEM_MEDIA_INCLUDE_ANDROID_CAMERA_METADATA_H
 
 #include <string.h>
 #include <stdint.h>
@@ -93,6 +93,25 @@ typedef struct camera_metadata_entry {
 } camera_metadata_entry_t;
 
 /**
+ * A read-only reference to a metadata entry in a buffer. Identical to
+ * camera_metadata_entry in layout
+ */
+typedef struct camera_metadata_ro_entry {
+    size_t   index;
+    uint32_t tag;
+    uint8_t  type;
+    size_t   count;
+    union {
+        const uint8_t *u8;
+        const int32_t *i32;
+        const float   *f;
+        const int64_t *i64;
+        const double  *d;
+        const camera_metadata_rational_t *r;
+    } data;
+} camera_metadata_ro_entry_t;
+
+/**
  * Size in bytes of each entry type
  */
 ANDROID_API
@@ -249,7 +268,7 @@ int append_camera_metadata(camera_metadata_t *dst, const camera_metadata_t *src)
  * can be freed with free_camera_metadata(). Returns NULL if cloning failed.
  */
 ANDROID_API
-camera_metadata_t *clone_camera_metadata(camera_metadata_t *src);
+camera_metadata_t *clone_camera_metadata(const camera_metadata_t *src);
 
 /**
  * Calculate the number of bytes of extra data a given metadata entry will take
@@ -311,6 +330,14 @@ int find_camera_metadata_entry(camera_metadata_t *src,
         camera_metadata_entry_t *entry);
 
 /**
+ * Find an entry with given tag value, but disallow editing the data
+ */
+ANDROID_API
+int find_camera_metadata_ro_entry(const camera_metadata_t *src,
+        uint32_t tag,
+        camera_metadata_ro_entry_t *entry);
+
+/**
  * Delete an entry at given index. This is an expensive operation, since it
  * requires repacking entries and possibly entry data. This also invalidates any
  * existing camera_metadata_entry.data pointers to this buffer. Sorting is
diff --git a/camera/src/camera_metadata.c b/camera/src/camera_metadata.c
index afbaac50..7bca3f4c 100644
--- a/camera/src/camera_metadata.c
+++ b/camera/src/camera_metadata.c
@@ -123,6 +123,8 @@ const char *camera_metadata_type_names[NUM_TYPES] = {
 
 camera_metadata_t *allocate_camera_metadata(size_t entry_capacity,
                                             size_t data_capacity) {
+    if (entry_capacity == 0) return NULL;
+
     size_t memory_needed = calculate_camera_metadata_size(entry_capacity,
                                                           data_capacity);
     void *buffer = malloc(memory_needed);
@@ -280,8 +282,9 @@ int append_camera_metadata(camera_metadata_t *dst,
     return OK;
 }
 
-camera_metadata_t *clone_camera_metadata(camera_metadata_t *src) {
+camera_metadata_t *clone_camera_metadata(const camera_metadata_t *src) {
     int res;
+    if (src == NULL) return NULL;
     camera_metadata_t *clone = allocate_camera_metadata(
         get_camera_metadata_entry_count(src),
         get_camera_metadata_data_count(src));
@@ -425,6 +428,14 @@ int find_camera_metadata_entry(camera_metadata_t *src,
             entry);
 }
 
+int find_camera_metadata_ro_entry(const camera_metadata_t *src,
+        uint32_t tag,
+        camera_metadata_ro_entry_t *entry) {
+    return find_camera_metadata_entry((camera_metadata_t*)src, tag,
+            (camera_metadata_entry_t*)entry);
+}
+
+
 int delete_camera_metadata_entry(camera_metadata_t *dst,
         size_t index) {
     if (dst == NULL) return ERROR;
@@ -611,12 +622,13 @@ void dump_indented_camera_metadata(const camera_metadata_t *metadata,
         int verbosity,
         int indentation) {
     if (metadata == NULL) {
-        ALOGE("%s: Metadata is null.", __FUNCTION__);
+        fdprintf(fd, "%*sDumping camera metadata array: Not allocated",
+                indentation, "");
         return;
     }
     unsigned int i;
     fdprintf(fd,
-            "%*sDumping camera metadata array. %d / %d entries, "
+            "%*sDumping camera metadata array: %d / %d entries, "
             "%d / %d bytes of extra data.\n", indentation, "",
             metadata->entry_count, metadata->entry_capacity,
             metadata->data_count, metadata->data_capacity);