Merge bitcoin/bitcoin#30883: build: Revert "Minimize I/O operations in `GenerateHeaderFrom{Json,Raw}.cmake`"

fdeb717e78fd55fbfda199c87002358bdc5895af Revert "build: Minimize I/O operations in `GenerateHeaderFrom{Json,Raw}.cmake`" (Hennadii Stepanov)

Pull request description:

  This reverts commit b07fe666f27e2b2515d2cb5a0339512045e64761 from https://github.com/bitcoin/bitcoin/pull/30842.

  Fixes https://github.com/bitcoin/bitcoin/issues/30881.

  Apparently, the `string(APPEND ...)` command isn't optimized for large strings.

ACKs for top commit:
  maflcko:
    review ACK fdeb717e78fd55fbfda199c87002358bdc5895af

Tree-SHA512: ad5c3d49d3395ab318edcd7c9a98090838bec0cd3c1f1cc6ebc6f4262df2494f605458b523251bf5e590bbcfda15ed963f0a814678135ce4cc2dca9a108d20c7

2 files changed, 21 insertions, 25 deletions

diff --git a/cmake/script/GenerateHeaderFromJson.cmake b/cmake/script/GenerateHeaderFromJson.cmake
index c0e895e9b3..53d1165272 100644
--- a/cmake/script/GenerateHeaderFromJson.cmake
+++ b/cmake/script/GenerateHeaderFromJson.cmake
@@ -5,24 +5,22 @@
 file(READ ${JSON_SOURCE_PATH} hex_content HEX)
 string(REGEX MATCHALL "([A-Za-z0-9][A-Za-z0-9])" bytes "${hex_content}")
 
-set(header_content "#include <string_view>\n")
-string(APPEND header_content "namespace json_tests{\n")
+file(WRITE ${HEADER_PATH} "#include <string_view>\n")
+file(APPEND ${HEADER_PATH} "namespace json_tests{\n")
 get_filename_component(json_source_basename ${JSON_SOURCE_PATH} NAME_WE)
-string(APPEND header_content "inline constexpr char detail_${json_source_basename}_bytes[]{\n")
+file(APPEND ${HEADER_PATH} "inline constexpr char detail_${json_source_basename}_bytes[]{\n")
 
 set(i 0)
 foreach(byte ${bytes})
   math(EXPR i "${i} + 1")
-  if(i EQUAL 8)
-    set(i 0)
-    string(APPEND header_content "0x${byte},\n")
+  math(EXPR remainder "${i} % 8")
+  if(remainder EQUAL 0)
+    file(APPEND ${HEADER_PATH} "0x${byte},\n")
   else()
-    string(APPEND header_content "0x${byte}, ")
+    file(APPEND ${HEADER_PATH} "0x${byte}, ")
   endif()
 endforeach()
 
-string(APPEND header_content "\n};\n")
-string(APPEND header_content "inline constexpr std::string_view ${json_source_basename}{std::begin(detail_${json_source_basename}_bytes), std::end(detail_${json_source_basename}_bytes)};")
-string(APPEND header_content "\n}")
-
-file(WRITE ${HEADER_PATH} "${header_content}")
+file(APPEND ${HEADER_PATH} "\n};\n")
+file(APPEND ${HEADER_PATH} "inline constexpr std::string_view ${json_source_basename}{std::begin(detail_${json_source_basename}_bytes), std::end(detail_${json_source_basename}_bytes)};")
+file(APPEND ${HEADER_PATH} "\n}")
diff --git a/cmake/script/GenerateHeaderFromRaw.cmake b/cmake/script/GenerateHeaderFromRaw.cmake
index 2a5140b9d6..18a6c2b407 100644
--- a/cmake/script/GenerateHeaderFromRaw.cmake
+++ b/cmake/script/GenerateHeaderFromRaw.cmake
@@ -5,25 +5,23 @@
 file(READ ${RAW_SOURCE_PATH} hex_content HEX)
 string(REGEX MATCHALL "([A-Za-z0-9][A-Za-z0-9])" bytes "${hex_content}")
 
-set(header_content "#include <cstddef>\n")
-string(APPEND header_content "#include <span>\n")
-string(APPEND header_content "namespace ${RAW_NAMESPACE} {\n")
+file(WRITE ${HEADER_PATH} "#include <cstddef>\n")
+file(APPEND ${HEADER_PATH} "#include <span>\n")
+file(APPEND ${HEADER_PATH} "namespace ${RAW_NAMESPACE} {\n")
 get_filename_component(raw_source_basename ${RAW_SOURCE_PATH} NAME_WE)
-string(APPEND header_content "inline constexpr std::byte detail_${raw_source_basename}_raw[]{\n")
+file(APPEND ${HEADER_PATH} "inline constexpr std::byte detail_${raw_source_basename}_raw[]{\n")
 
 set(i 0)
 foreach(byte ${bytes})
   math(EXPR i "${i} + 1")
-  if(i EQUAL 8)
-    set(i 0)
-    string(APPEND header_content "std::byte{0x${byte}},\n")
+  math(EXPR remainder "${i} % 8")
+  if(remainder EQUAL 0)
+    file(APPEND ${HEADER_PATH} "std::byte{0x${byte}},\n")
   else()
-    string(APPEND header_content "std::byte{0x${byte}}, ")
+    file(APPEND ${HEADER_PATH} "std::byte{0x${byte}}, ")
   endif()
 endforeach()
 
-string(APPEND header_content "\n};\n")
-string(APPEND header_content "inline constexpr std::span ${raw_source_basename}{detail_${raw_source_basename}_raw};\n")
-string(APPEND header_content "}")
-
-file(WRITE ${HEADER_PATH} "${header_content}")
+file(APPEND ${HEADER_PATH} "\n};\n")
+file(APPEND ${HEADER_PATH} "inline constexpr std::span ${raw_source_basename}{detail_${raw_source_basename}_raw};\n")
+file(APPEND ${HEADER_PATH} "}")