From d89aea73e2ff9c28516ada9a31fed4ba5fb42c05 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timur=20Krist=C3=B3f?= <timur.kristof@gmail.com>
Date: Fri, 17 Feb 2023 20:14:00 +0100
Subject: [PATCH] util: Add util_format_get_array.
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This is a poor man's version of MESA_ARRAY_FORMAT.
Implemented based on a gigantic switch-case
with some help from the C preprocessor.
Thank you, preprocessor!

Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Faith Ekstrand <faith.ekstrand@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21692>
---
 src/util/format/u_format.c | 67 ++++++++++++++++++++++++++++++++++++++
 src/util/format/u_format.h |  6 ++++
 2 files changed, 73 insertions(+)

diff --git a/src/util/format/u_format.c b/src/util/format/u_format.c
index a1edafe2d10..bfbefc6176d 100644
--- a/src/util/format/u_format.c
+++ b/src/util/format/u_format.c
@@ -1367,3 +1367,70 @@ util_format_rgbx_to_rgba(enum pipe_format format)
    }
    }
 }
+
+enum pipe_format
+util_format_get_array(const enum util_format_type type, const unsigned bits,
+                      const unsigned nr_components, const bool normalized,
+                      const bool pure_integer)
+{
+#define CASE_BY_BIT_SWITCH_BY_NR_COMPONENTS_1TO4(TYPE, BITS, NR_VAR) \
+   case BITS: \
+      switch (NR_VAR) { \
+      case 1: \
+         return PIPE_FORMAT_R##BITS##_##TYPE; \
+      case 2: \
+         return PIPE_FORMAT_R##BITS##G##BITS##_##TYPE; \
+      case 3: \
+         return PIPE_FORMAT_R##BITS##G##BITS##B##BITS##_##TYPE; \
+      case 4: \
+         return PIPE_FORMAT_R##BITS##G##BITS##B##BITS##A##BITS##_##TYPE; \
+      default: \
+         return PIPE_FORMAT_NONE; \
+      }
+
+#define SWITCH_BY_BITS_CASEX3(TYPE, BITS_VAR, BITS1, BITS2, BITS3, NR_VAR) \
+   switch (BITS_VAR) { \
+   CASE_BY_BIT_SWITCH_BY_NR_COMPONENTS_1TO4(TYPE, BITS1, NR_VAR) \
+   CASE_BY_BIT_SWITCH_BY_NR_COMPONENTS_1TO4(TYPE, BITS2, NR_VAR) \
+   CASE_BY_BIT_SWITCH_BY_NR_COMPONENTS_1TO4(TYPE, BITS3, NR_VAR) \
+   default: \
+      return PIPE_FORMAT_NONE; \
+   }
+
+#define SWITCH_BY_BITS_CASEX4(TYPE, BITS_VAR, BITS1, BITS2, BITS3, BITS4, NR_VAR) \
+   switch (BITS_VAR) { \
+   CASE_BY_BIT_SWITCH_BY_NR_COMPONENTS_1TO4(TYPE, BITS1, NR_VAR) \
+   CASE_BY_BIT_SWITCH_BY_NR_COMPONENTS_1TO4(TYPE, BITS2, NR_VAR) \
+   CASE_BY_BIT_SWITCH_BY_NR_COMPONENTS_1TO4(TYPE, BITS3, NR_VAR) \
+   CASE_BY_BIT_SWITCH_BY_NR_COMPONENTS_1TO4(TYPE, BITS4, NR_VAR) \
+   default: \
+      return PIPE_FORMAT_NONE; \
+   }
+
+   switch (type) {
+   case UTIL_FORMAT_TYPE_UNSIGNED:
+      if (normalized)
+         SWITCH_BY_BITS_CASEX3(UNORM, bits, 8, 16, 32, nr_components)
+      else if (!pure_integer)
+         SWITCH_BY_BITS_CASEX3(USCALED, bits, 8, 16, 32, nr_components)
+      else
+         SWITCH_BY_BITS_CASEX4(UINT, bits, 8, 16, 32, 64, nr_components)
+   case UTIL_FORMAT_TYPE_SIGNED:
+      if (normalized)
+         SWITCH_BY_BITS_CASEX3(SNORM, bits, 8, 16, 32, nr_components)
+      else if (!pure_integer)
+         SWITCH_BY_BITS_CASEX3(SSCALED, bits, 8, 16, 32, nr_components)
+      else
+         SWITCH_BY_BITS_CASEX4(SINT, bits, 8, 16, 32, 64, nr_components)
+   case UTIL_FORMAT_TYPE_FLOAT:
+      SWITCH_BY_BITS_CASEX3(FLOAT, bits, 16, 32, 64, nr_components)
+   default:
+      return PIPE_FORMAT_NONE;
+   }
+
+#undef CASE_BY_BIT_SWITCH_BY_NR_COMPONENTS_1TO4
+#undef SWITCH_BY_BITS_CASEX3
+#undef SWITCH_BY_BITS_CASEX4
+
+   return PIPE_FORMAT_NONE;
+}
diff --git a/src/util/format/u_format.h b/src/util/format/u_format.h
index 035a7e0bba8..439c3ceb0cc 100644
--- a/src/util/format/u_format.h
+++ b/src/util/format/u_format.h
@@ -1706,6 +1706,12 @@ util_format_snorm_to_unorm(enum pipe_format format);
 enum pipe_format
 util_format_rgbx_to_rgba(enum pipe_format format);
 
+/* Returns the pipe format for the given array type, bitsize and component count. */
+enum pipe_format
+util_format_get_array(const enum util_format_type type, const unsigned bits,
+                      const unsigned nr_components, const bool normalized,
+                      const bool pure_integer);
+
 #ifdef __cplusplus
 } // extern "C" {
 #endif