backport: build(windows): vendor xxd.c (#36755)

backport https://github.com/neovim/neovim/pull/36746

Problem:
Currently we fetch a prebuilt xxd.exe from neovim/deps for Windows,
which is not ideal in terms of obviousness, misses updates, and is
clumsy to update.

Solution:
Similar to tee.c (#36363), vendor xxd.c from Vim and build it as part
of the Neovim build process. This makes the source obvious, enables
analyzer checks, and simplifies updates.

Fixes #36664

Co-authored-by: benarcher2691 <ben.archer2691@gmail.com>

CMakeLists.txt

@@ -289,6 +289,7 @@ add_dependencies(nvim nvim_bin nvim_runtime_deps nvim_runtime)
 
 add_subdirectory(src/nvim)
 add_subdirectory(src/tee)
+add_subdirectory(src/xxd)
 add_subdirectory(cmake.config)
 add_subdirectory(runtime)
 add_subdirectory(test)

src/nvim/CMakeLists.txt

@@ -450,7 +450,10 @@ foreach(hfile ${NVIM_HEADERS})
 endforeach()
 
 list(APPEND LINT_NVIM_SOURCES ${NVIM_SOURCES} ${NVIM_HEADERS})
-list(APPEND LINT_NVIM_SOURCES ${PROJECT_SOURCE_DIR}/src/tee/tee.c)
+list(APPEND LINT_NVIM_SOURCES
+  ${PROJECT_SOURCE_DIR}/src/tee/tee.c
+  ${PROJECT_SOURCE_DIR}/src/xxd/xxd.c
+)
 
 # Log level (NVIM_LOG_DEBUG in log.h)
 if(CI_BUILD)
@@ -850,7 +853,7 @@ target_link_libraries(libnvim PRIVATE main_lib PUBLIC libuv)
 
 find_program(CLANG_TIDY_PRG clang-tidy)
 mark_as_advanced(CLANG_TIDY_PRG)
-set(EXCLUDE_CLANG_TIDY typval_encode.c.h ui_events.in.h)
+set(EXCLUDE_CLANG_TIDY typval_encode.c.h ui_events.in.h xxd/xxd.c)
 if(WIN32)
   list(APPEND EXCLUDE_CLANG_TIDY
     os/pty_proc_unix.h
@@ -912,7 +915,8 @@ add_glob_target(
   FLAGS --output=${LINT_OUTPUT_FORMAT}
   FILES ${LINT_NVIM_SOURCES}
   EXCLUDE
-    tui/terminfo_defs.h)
+    tui/terminfo_defs.h
+    xxd/xxd.c)
 
 set(UNCRUSTIFY_PRG ${DEPS_BIN_DIR}/uncrustify)
 set(UNCRUSTIFY_CONFIG ${PROJECT_SOURCE_DIR}/src/uncrustify.cfg)

src/xxd/CMakeLists.txt

@@ -0,0 +1,12 @@
+add_executable(xxd xxd.c)
+
+# xxd has to be in the same directory as the nvim executable
+set_target_properties(xxd PROPERTIES
+  RUNTIME_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/bin"
+)
+
+if(WIN32)
+  install(TARGETS xxd
+    RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}"
+  )
+endif()

test/functional/editor/xxd_spec.lua

@@ -0,0 +1,19 @@
+local t = require('test.testutil')
+local n = require('test.functional.testnvim')()
+
+local eq = t.eq
+local clear = n.clear
+local fn = n.fn
+local testprg = n.testprg
+
+describe('xxd', function()
+  before_each(clear)
+
+  it('works', function()
+    -- Round-trip test: encode then decode should return original
+    local input = 'hello'
+    local encoded = fn.system({ testprg('xxd') }, input)
+    local decoded = fn.system({ testprg('xxd'), '-r' }, encoded)
+    eq(input, decoded)
+  end)
+end)