Reduce reallocations in exif parsing

Instead of reallocating lists element by element, increase the
allocated list size exponentially.

diff --git a/ext/exif/exif.c b/ext/exif/exif.c
index 418e658bf78d0b7bff2bce297ecf9d1e5d34aa3a..53087417aad1bebcdb2216cbff1b175acf750355 100644 (file)
--- a/ext/exif/exif.c
+++ b/ext/exif/exif.c
@@ -1760,6 +1760,7 @@ typedef struct {
 
 typedef struct {
        int                 count;
+       int                 alloc_count;
        image_info_data         *list;
 } image_info_list;
 /* }}} */
@@ -1880,6 +1881,7 @@ typedef struct {
 
 typedef struct {
        int             count;
+       int             alloc_count;
        file_section    *list;
 } file_section_list;
 
@@ -2004,11 +2006,14 @@ typedef struct {
 */
 static int exif_file_sections_add(image_info_type *ImageInfo, int type, size_t size, uchar *data)
 {
-       file_section    *tmp;
-       int             count = ImageInfo->file.count;
+       int count = ImageInfo->file.count;
+       if (count == ImageInfo->file.alloc_count) {
+               int new_alloc_count = ImageInfo->file.alloc_count ? ImageInfo->file.alloc_count * 2 : 1;
+               ImageInfo->file.list = safe_erealloc(
+                       ImageInfo->file.list, new_alloc_count, sizeof(file_section), 0);
+               ImageInfo->file.alloc_count = new_alloc_count;
+       }
 
-       tmp = safe_erealloc(ImageInfo->file.list, (count+1), sizeof(file_section), 0);
-       ImageInfo->file.list = tmp;
        ImageInfo->file.list[count].type = 0xFFFF;
        ImageInfo->file.list[count].data = NULL;
        ImageInfo->file.list[count].size = 0;
@@ -2064,6 +2069,16 @@ static int exif_file_sections_free(image_info_type *ImageInfo)
 }
 /* }}} */
 
+static image_info_data *exif_alloc_image_info_data(image_info_list *info_list) {
+       if (info_list->count == info_list->alloc_count) {
+               int new_alloc_count = info_list->alloc_count ? info_list->alloc_count * 2 : 1;
+               info_list->list = safe_erealloc(
+                       info_list->list, new_alloc_count, sizeof(image_info_data), 0);
+               info_list->alloc_count = new_alloc_count;
+       }
+       return &info_list->list[info_list->count++];
+}
+
 /* {{{ exif_iif_add_value
  Add a value to image_info
 */
@@ -2073,16 +2088,12 @@ static void exif_iif_add_value(image_info_type *image_info, int section_index, c
        void *vptr, *vptr_end;
        image_info_value *info_value;
        image_info_data  *info_data;
-       image_info_data  *list;
 
        if (length < 0) {
                return;
        }
 
-       list = safe_erealloc(image_info->info_list[section_index].list, (image_info->info_list[section_index].count+1), sizeof(image_info_data), 0);
-       image_info->info_list[section_index].list = list;
-
-       info_data  = &image_info->info_list[section_index].list[image_info->info_list[section_index].count];
+       info_data = exif_alloc_image_info_data(&image_info->info_list[section_index]);
        memset(info_data, 0, sizeof(image_info_data));
        info_data->tag    = tag;
        info_data->format = format;
@@ -2205,7 +2216,6 @@ static void exif_iif_add_value(image_info_type *image_info, int section_index, c
                        }
        }
        image_info->sections_found |= 1<<section_index;
-       image_info->info_list[section_index].count++;
 }
 /* }}} */
 
@@ -2223,20 +2233,13 @@ static void exif_iif_add_tag(image_info_type *image_info, int section_index, cha
 */
 static void exif_iif_add_int(image_info_type *image_info, int section_index, char *name, int value)
 {
-       image_info_data  *info_data;
-       image_info_data  *list;
-
-       list = safe_erealloc(image_info->info_list[section_index].list, (image_info->info_list[section_index].count+1), sizeof(image_info_data), 0);
-       image_info->info_list[section_index].list = list;
-
-       info_data  = &image_info->info_list[section_index].list[image_info->info_list[section_index].count];
+       image_info_data *info_data = exif_alloc_image_info_data(&image_info->info_list[section_index]);
        info_data->tag    = TAG_NONE;
        info_data->format = TAG_FMT_SLONG;
        info_data->length = 1;
        info_data->name   = estrdup(name);
        info_data->value.i = value;
        image_info->sections_found |= 1<<section_index;
-       image_info->info_list[section_index].count++;
 }
 /* }}} */
 
@@ -2245,20 +2248,15 @@ static void exif_iif_add_int(image_info_type *image_info, int section_index, cha
 */
 static void exif_iif_add_str(image_info_type *image_info, int section_index, char *name, char *value)
 {
-       image_info_data  *info_data;
-       image_info_data  *list;
-
        if (value) {
-               list = safe_erealloc(image_info->info_list[section_index].list, (image_info->info_list[section_index].count+1), sizeof(image_info_data), 0);
-               image_info->info_list[section_index].list = list;
-               info_data  = &image_info->info_list[section_index].list[image_info->info_list[section_index].count];
+               image_info_data *info_data =
+                       exif_alloc_image_info_data(&image_info->info_list[section_index]);
                info_data->tag    = TAG_NONE;
                info_data->format = TAG_FMT_STRING;
                info_data->length = 1;
                info_data->name   = estrdup(name);
                info_data->value.s = estrdup(value);
                image_info->sections_found |= 1<<section_index;
-               image_info->info_list[section_index].count++;
        }
 }
 /* }}} */
@@ -2286,13 +2284,9 @@ static void exif_iif_add_fmt(image_info_type *image_info, int section_index, cha
 */
 static void exif_iif_add_buffer(image_info_type *image_info, int section_index, char *name, int length, char *value)
 {
-       image_info_data  *info_data;
-       image_info_data  *list;
-
        if (value) {
-               list = safe_erealloc(image_info->info_list[section_index].list, (image_info->info_list[section_index].count+1), sizeof(image_info_data), 0);
-               image_info->info_list[section_index].list = list;
-               info_data  = &image_info->info_list[section_index].list[image_info->info_list[section_index].count];
+               image_info_data *info_data =
+                       exif_alloc_image_info_data(&image_info->info_list[section_index]);
                info_data->tag    = TAG_NONE;
                info_data->format = TAG_FMT_UNDEFINED;
                info_data->length = length;
@@ -2301,7 +2295,6 @@ static void exif_iif_add_buffer(image_info_type *image_info, int section_index,
                memcpy(info_data->value.s, value, length);
                info_data->value.s[length] = 0;
                image_info->sections_found |= 1<<section_index;
-               image_info->info_list[section_index].count++;
        }
 }
 /* }}} */