From 48dbfba17a5f0832ef655f782ee25109b273ff1f Mon Sep 17 00:00:00 2001
From: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Date: Wed, 15 Jan 2025 15:39:51 -0500
Subject: [PATCH] util: add u_printf_hash helper

for hash-based printf. this just shells out to XXH - convenience wrapper.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Jesse Natalie <jenatali@microsoft.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/33067>
---
 src/util/u_printf.c | 28 ++++++++++++++++++++++++++++
 src/util/u_printf.h |  2 ++
 2 files changed, 30 insertions(+)

diff --git a/src/util/u_printf.c b/src/util/u_printf.c
index b432e8925e6..a9c3903e967 100644
--- a/src/util/u_printf.c
+++ b/src/util/u_printf.c
@@ -35,6 +35,9 @@
 #include "u_math.h"
 #include "u_printf.h"
 
+#define XXH_INLINE_ALL
+#include "util/xxhash.h"
+
 /* Some versions of MinGW are missing _vscprintf's declaration, although they
  * still provide the symbol in the import library. */
 #ifdef __MINGW32__
@@ -332,3 +335,28 @@ u_printf_deserialize_info(void *mem_ctx,
 
    return printf_info;
 }
+
+/*
+ * Hash the format string, allowing the driver to pool format strings.
+ *
+ * Post-condition: hash is nonzero. This is convenient.
+ */
+uint32_t
+u_printf_hash(const u_printf_info *info)
+{
+   struct blob blob;
+   blob_init(&blob);
+   u_printf_serialize_info(&blob, info, 1);
+   uint32_t hash = XXH32(blob.data, blob.size, 0);
+   blob_finish(&blob);
+
+   /* Force things away from zero. This weakens the hash only slightly, as
+    * there's only a 2^-31 probability of hashing to either hash=0 or hash=1.
+    */
+   if (hash == 0) {
+      hash = 1;
+   }
+
+   assert(hash != 0);
+   return hash;
+}
diff --git a/src/util/u_printf.h b/src/util/u_printf.h
index a89a5041105..427301ed7ba 100644
--- a/src/util/u_printf.h
+++ b/src/util/u_printf.h
@@ -49,6 +49,8 @@ u_printf_info *u_printf_deserialize_info(void *mem_ctx,
                                          struct blob_reader *blob,
                                          unsigned *printf_info_count);
 
+uint32_t u_printf_hash(const u_printf_info *info);
+
 struct u_printf_ctx {
    simple_mtx_t lock;
    void *bo;