glsl: Add initial functions to implement an on-disk cache

This code provides for an on-disk cache of objects. Objects are stored
and retrieved via names that are arbitrary 20-byte sequences,
(intended to be SHA-1 hashes of something identifying for the
content). The directory used for the cache can be specified by means
of environment variables in the following priority order:

	$MESA_GLSL_CACHE_DIR
	$XDG_CACHE_HOME/mesa
	<user-home-directory>/.cache/mesa

By default the cache will be limited to a maximum size of 1GB. The
environment variable:

	$MESA_GLSL_CACHE_MAX_SIZE

can be set (at the time of GL context creation) to choose some other
size. This variable is a number that can optionally be followed by
'K', 'M', or 'G' to select a size in kilobytes, megabytes, or
gigabytes. By default, an unadorned value will be interpreted as
gigabytes.

The cache will be entirely disabled at runtime if the variable
MESA_GLSL_CACHE_DISABLE is set at the time of GL context creation.

Many thanks to Kristian Høgsberg <[email protected]> for the initial
implementation of code that led to this patch. In particular, the idea
of using an mmapped file, (indexed by a portion of the SHA-1), for the
efficent implementation of cache_has_key was entirely his
idea. Kristian also provided some very helpful advice in discussions
regarding various race conditions to be avoided in this code.

Signed-off-by: Timothy Arceri <[email protected]>
Reviewed-by: Eric Anholt <[email protected]>

1 files changed, 4 insertions, 0 deletions

diff --git a/src/compiler/Makefile.sources b/src/compiler/Makefile.sources
index f5b4f9c0b98..712b33aa74c 100644
--- a/src/compiler/Makefile.sources
+++ b/src/compiler/Makefile.sources
@@ -136,6 +136,10 @@ LIBGLSL_FILES = \
 	glsl/s_expression.cpp \
 	glsl/s_expression.h
 
+LIBGLSL_SHADER_CACHE_FILES = \
+	glsl/cache.c \
+	glsl/cache.h
+
 # glsl_compiler
 
 GLSL_COMPILER_CXX_FILES = \