From e835c889a178d2bdfcf52220e461ecfcd9067afb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C5=99emysl=20Eric=20Janouch?= <p@janouch.name>
Date: Mon, 15 Nov 2021 10:16:10 +0100
Subject: Don't use a side buffer to load thumbnails

Undoing part of a recent commit.
---
 fastiv-io.c | 49 ++++++++++++++++++++++++-------------------------
 1 file changed, 24 insertions(+), 25 deletions(-)

diff --git a/fastiv-io.c b/fastiv-io.c
index 64bbb3c..d63d336 100644
--- a/fastiv-io.c
+++ b/fastiv-io.c
@@ -645,12 +645,12 @@ read_spng_thumbnail(
 	const gchar *path, const gchar *uri, time_t mtime, GError **error)
 {
 	FILE *fp;
+	cairo_surface_t *result = NULL;
 	if (!(fp = fopen(path, "rb"))) {
 		set_error(error, g_strerror(errno));
 		return NULL;
 	}
 
-	cairo_surface_t *result = NULL;
 	errno = 0;
 	spng_ctx *ctx = spng_ctx_new(0);
 	if (!ctx) {
@@ -671,21 +671,6 @@ read_spng_thumbnail(
 		goto fail;
 	}
 
-	uint32_t *data = g_malloc0(size);
-	if ((err = spng_decode_image(ctx, data, size, SPNG_FMT_RGBA8,
-		SPNG_DECODE_TRNS | SPNG_DECODE_GAMMA))) {
-		set_error(error, spng_strerror(err));
-		goto fail_data;
-	}
-
-	// The specification does not say where the required metadata should be,
-	// it could very well be broken up into two parts.
-	if (check_spng_thumbnail(ctx, uri, mtime, &err) != true) {
-		set_error(
-			error, err ? spng_strerror(err) : "mismatch or not a thumbnail");
-		goto fail_data;
-	}
-
 	struct spng_ihdr ihdr = {};
 	spng_get_ihdr(ctx, &ihdr);
 	cairo_surface_t *surface = cairo_image_surface_create(
@@ -694,39 +679,53 @@ read_spng_thumbnail(
 	cairo_status_t surface_status = cairo_surface_status(surface);
 	if (surface_status != CAIRO_STATUS_SUCCESS) {
 		set_error(error, cairo_status_to_string(surface_status));
-		cairo_surface_destroy(surface);
 		goto fail_data;
 	}
 
+	uint32_t *data = (uint32_t *) cairo_image_surface_get_data(surface);
 	g_assert((size_t) cairo_image_surface_get_stride(surface) *
 		cairo_image_surface_get_height(surface) == size);
 
-	// pixman can be mildly abused to do this operation, but it won't be faster.
-	uint32_t *output = (uint32_t *) cairo_image_surface_get_data(surface);
 	cairo_surface_flush(surface);
+	if ((err = spng_decode_image(ctx, data, size, SPNG_FMT_RGBA8,
+		SPNG_DECODE_TRNS | SPNG_DECODE_GAMMA))) {
+		set_error(error, spng_strerror(err));
+		goto fail_data;
+	}
 
+	// The specification does not say where the required metadata should be,
+	// it could very well be broken up into two parts.
+	if (check_spng_thumbnail(ctx, uri, mtime, &err) != true) {
+		set_error(
+			error, err ? spng_strerror(err) : "mismatch or not a thumbnail");
+		goto fail_data;
+	}
+
+	// pixman can be mildly abused to do this operation, but it won't be faster.
 	struct spng_trns trns = {};
 	if (ihdr.color_type == SPNG_COLOR_TYPE_GRAYSCALE_ALPHA ||
 		ihdr.color_type == SPNG_COLOR_TYPE_TRUECOLOR_ALPHA ||
 		!spng_get_trns(ctx, &trns)) {
-		for (size_t i = size / sizeof *output; i--; ) {
+		for (size_t i = size / sizeof *data; i--; ) {
 			const uint8_t *unit = (const uint8_t *) &data[i],
 				a = unit[3],
 				b = unit[2] * a / 255,
 				g = unit[1] * a / 255,
 				r = unit[0] * a / 255;
-			output[i] = a << 24 | r << 16 | g << 8 | b;
+			data[i] = a << 24 | r << 16 | g << 8 | b;
 		}
 	} else {
-		for (size_t i = size / sizeof *output; i--; ) {
-			uint32_t x = g_ntohl(data[i]);
-			output[i] = x << 24 | x >> 8;
+		for (size_t i = size / sizeof *data; i--; ) {
+			uint32_t rgba = g_ntohl(data[i]);
+			data[i] = rgba << 24 | rgba >> 8;
 		}
 	}
 
 	cairo_surface_mark_dirty((result = surface));
+
 fail_data:
-	free(data);
+	if (!result)
+		cairo_surface_destroy(surface);
 fail:
 	spng_ctx_free(ctx);
 fail_init:
-- 
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