From 00f7bf91d85198d5c42ece1e2a5dd63e47aa4645 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lo=C3=AFc=20Molinari?= <loic.molinari@collabora.com>
Date: Thu, 10 Oct 2024 11:30:42 +0200
Subject: [PATCH] gl-renderer: Add extension flag parser
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This new utility parses extension strings and fills a bitfield of
matched flags. This will be used to store EGL and GL extension flags.

Signed-off-by: Loïc Molinari <loic.molinari@collabora.com>
---
 libweston/renderer-gl/gl-renderer-internal.h | 13 +++++
 libweston/renderer-gl/gl-renderer.c          | 56 ++++++++++++++++++++
 2 files changed, 69 insertions(+)

diff --git a/libweston/renderer-gl/gl-renderer-internal.h b/libweston/renderer-gl/gl-renderer-internal.h
index 9c7103ed3..99ad1bbab 100644
--- a/libweston/renderer-gl/gl-renderer-internal.h
+++ b/libweston/renderer-gl/gl-renderer-internal.h
@@ -54,6 +54,8 @@
 /* Max number of images per buffer. */
 #define SHADER_INPUT_TEX_MAX 3
 
+#define EXT(string, flag) { string, ARRAY_LENGTH(string) - 1, (uint64_t) flag }
+
 /* Keep the following in sync with vertex.glsl. */
 enum gl_shader_texcoord_input {
 	SHADER_TEXCOORD_INPUT_ATTRIB = 0,
@@ -107,6 +109,12 @@ static_assert(TEX_UNIT_LAST < 8, "OpenGL ES 2.0 requires at least 8 texture "
 	      "GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS check at display creation "
 	      "to require more.");
 
+struct gl_extension_table {
+	const char *str;
+	size_t len;
+	uint64_t flag;
+};
+
 /** GL shader requirements key
  *
  * This structure is used as a binary blob key for building and searching
@@ -325,6 +333,11 @@ gl_version_minor(uint32_t ver)
 	return ver & 0xffff;
 }
 
+void
+gl_extensions_add(const struct gl_extension_table *table,
+		  const char *extensions,
+		  uint64_t *flags_out);
+
 static inline struct gl_renderer *
 get_renderer(struct weston_compositor *ec)
 {
diff --git a/libweston/renderer-gl/gl-renderer.c b/libweston/renderer-gl/gl-renderer.c
index 1ecfceded..08665bd16 100644
--- a/libweston/renderer-gl/gl-renderer.c
+++ b/libweston/renderer-gl/gl-renderer.c
@@ -424,6 +424,62 @@ struct yuv_format_descriptor yuv_formats[] = {
 	}
 };
 
+/* Add extension flags to the bitfield that 'flags_out' points to. 'table'
+ * stores extension names and flags to check for and 'extensions' is the list
+ * usually returned by the EGL or GL implementation. New flags are stored using
+ * a binary OR in order to keep flags set from a previous call. Caller must
+ * ensure the bitfield is set to 0 at first call.
+ */
+void
+gl_extensions_add(const struct gl_extension_table *table,
+		  const char *extensions,
+		  uint64_t *flags_out)
+{
+	struct { const char *str; size_t len; } *map;
+	size_t i = 0, n = 0;
+	uint64_t flags = 0;
+	char prev_char = ' ';
+
+	/* Get number of extensions. */
+	while (extensions[i]) {
+		if (prev_char == ' ' && extensions[i] != ' ')
+			n++;
+		prev_char = extensions[i++];
+	}
+
+	if (n == 0)
+		return;
+
+	/* Allocate data structure mapping each extension with their length. */
+	map = xmalloc(n * sizeof *map);
+	prev_char = ' ';
+	i = n = 0;
+	while (prev_char) {
+		if (extensions[i] != ' ' && extensions[i] != '\0') {
+			if (prev_char == ' ')
+				map[n].str = &extensions[i];
+		} else if (prev_char != ' ') {
+			map[n].len = &extensions[i] - map[n].str;
+			n++;
+		}
+		prev_char = extensions[i++];
+	}
+
+	/* Match extensions with table. */
+	for (; table->str; table++) {
+		for (i = 0; i < n; i++) {
+			if (table->len == map[i].len &&
+			    !strncmp(table->str, map[i].str, table->len)) {
+				flags |= table->flag;
+				break;
+			}
+		}
+	}
+
+	*flags_out |= flags;
+	free(map);
+}
+
 static void
 timeline_begin_render_query(struct gl_renderer *gr, GLuint query)
 {