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misc: dynamic linking code refactor #141

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Merged
merged 1 commit into from
Aug 16, 2025
Merged

misc: dynamic linking code refactor #141

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105 changes: 53 additions & 52 deletions build.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -187,6 +187,31 @@ impl callbacks::ParseCallbacks for FilterCargoCallbacks {
}
}

#[derive(Clone, Copy)]
enum FFmpegLinkMode {
Static,
Dynamic,
}

impl From<String> for FFmpegLinkMode {
fn from(value: String) -> Self {
match &*value {
"static" => FFmpegLinkMode::Static,
"dynamic" => FFmpegLinkMode::Dynamic,
_ => panic!("Invalid FFMPEG_LINK_MODE value, expected [static,dynamic]"),
}
}
}

impl std::fmt::Display for FFmpegLinkMode {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
match self {
FFmpegLinkMode::Static => write!(f, "static"),
FFmpegLinkMode::Dynamic => write!(f, "dylib"),
}
}
}

fn use_prebuilt_binding(from: &Path, to: &Path) {
fs::copy(from, to).expect("Prebuilt binding file failed to be copied.");
}
Expand Down Expand Up @@ -242,31 +267,24 @@ fn generate_bindings(ffmpeg_include_dir: &Path, headers: &[PathBuf]) -> Bindings
.expect("Binding generation failed.")
}

fn linking_with_libs_dir(library_names: &[&str], ffmpeg_libs_dir: &Path, mode: FfmpegLinkMode) {
fn linking_with_libs_dir(library_names: &[&str], ffmpeg_libs_dir: &Path, mode: FFmpegLinkMode) {
println!("cargo:rustc-link-search=native={ffmpeg_libs_dir}");
for library_name in library_names {
println!(
"cargo:rustc-link-lib={}={library_name}",
match mode {
FfmpegLinkMode::Dynamic => "dylib",
FfmpegLinkMode::Static => "static",
}
);
println!("cargo:rustc-link-lib={mode}={library_name}");
}
}

#[derive(Clone, Copy)]
enum FfmpegLinkMode {
Static,
Dynamic,
fn linking_with_single_lib(library_name: &str, ffmpeg_lib_dir: &Path, mode: FFmpegLinkMode) {
println!("cargo:rustc-link-search=native={ffmpeg_lib_dir}");
println!("cargo:rustc-link-lib={mode}={library_name}");
}

#[allow(dead_code)]
pub struct EnvVars {
docs_rs: Option<String>,
out_dir: Option<PathBuf>,
ffmpeg_include_dir: Option<PathBuf>,
ffmpeg_link_mode: Option<FfmpegLinkMode>,
ffmpeg_link_mode: Option<FFmpegLinkMode>,
ffmpeg_dll_path: Option<PathBuf>,
ffmpeg_pkg_config_path: Option<PathBuf>,
ffmpeg_libs_dir: Option<PathBuf>,
Expand All @@ -291,12 +309,7 @@ impl EnvVars {
ffmpeg_pkg_config_path: env::var("FFMPEG_PKG_CONFIG_PATH").ok().map(remove_verbatim),
ffmpeg_libs_dir: env::var("FFMPEG_LIBS_DIR").ok().map(remove_verbatim),
ffmpeg_binding_path: env::var("FFMPEG_BINDING_PATH").ok().map(remove_verbatim),
ffmpeg_link_mode: match env::var("FFMPEG_LINK_MODE").ok().as_deref() {
Some("static") => Some(FfmpegLinkMode::Static),
Some("dynamic") => Some(FfmpegLinkMode::Dynamic),
Some(r) => panic!("invalid FFMPEG_LINK_MODE value {r}, expected [static,dynamic]"),
None => None,
},
ffmpeg_link_mode: env::var("FFMPEG_LINK_MODE").ok().map(Into::into),
}
}
}
Expand Down Expand Up @@ -379,41 +392,29 @@ mod vcpkg_linking {
}
}

fn dynamic_linking(mut env_vars: EnvVars) {
fn dynamic_linking(env_vars: EnvVars) {
let ffmpeg_dll_path = env_vars.ffmpeg_dll_path.as_ref().unwrap();
if ffmpeg_dll_path.is_dir() {
if env_vars.ffmpeg_libs_dir.is_none() {
env_vars.ffmpeg_libs_dir = Some(ffmpeg_dll_path.clone());
}
if env_vars.ffmpeg_link_mode.is_none() {
env_vars.ffmpeg_link_mode = Some(FfmpegLinkMode::Dynamic);
}

return linking(env_vars);
linking_with_libs_dir(&*LIBS, ffmpeg_dll_path, FFmpegLinkMode::Dynamic);
} else {
let (lib_name, ffmpeg_dll_dir) = (
ffmpeg_dll_path
.file_stem()
.map(|stem| {
if cfg!(target_os = "windows") {
stem
} else {
stem.trim_start_matches("lib")
}
})
.unwrap()
.to_string(),
ffmpeg_dll_path.parent().unwrap().to_path_buf(),
);
linking_with_single_lib(&lib_name, &ffmpeg_dll_dir, FFmpegLinkMode::Dynamic);
}

let output_binding_path = &env_vars.out_dir.as_ref().unwrap().join("binding.rs");

// Extract dll name and the dir the dll is in.
let (ffmpeg_dll_name, ffmpeg_dll_dir) = {
let mut ffmpeg_dll_path = PathBuf::from(ffmpeg_dll_path);
// Without extension.
let ffmpeg_dll_filename = ffmpeg_dll_path.file_stem().unwrap();
let ffmpeg_dll_name = if cfg!(target_os = "windows") {
ffmpeg_dll_filename
} else {
ffmpeg_dll_filename.trim_start_matches("lib")
}
.to_string();
// Remove file name.
ffmpeg_dll_path.pop();
let ffmpeg_dll_path = ffmpeg_dll_path.to_string();
(ffmpeg_dll_name, ffmpeg_dll_path)
};

println!("cargo:rustc-link-lib=dylib={}", ffmpeg_dll_name);
println!("cargo:rustc-link-search=native={}", ffmpeg_dll_dir);

if let Some(ffmpeg_binding_path) = env_vars.ffmpeg_binding_path.as_ref() {
use_prebuilt_binding(ffmpeg_binding_path, output_binding_path);
} else if let Some(ffmpeg_include_dir) = env_vars.ffmpeg_include_dir.as_ref() {
Expand Down Expand Up @@ -466,7 +467,7 @@ fn linking(env_vars: EnvVars) {
linking_with_libs_dir(
&*LIBS,
ffmpeg_libs_dir,
env_vars.ffmpeg_link_mode.unwrap_or(FfmpegLinkMode::Static),
env_vars.ffmpeg_link_mode.unwrap_or(FFmpegLinkMode::Static),
);
if let Some(ffmpeg_binding_path) = env_vars.ffmpeg_binding_path.as_ref() {
use_prebuilt_binding(ffmpeg_binding_path, output_binding_path);
Expand Down Expand Up @@ -528,7 +529,7 @@ Enable `link_vcpkg_ffmpeg` feature if you want to link ffmpeg libraries installe
linking_with_libs_dir(
&*LIBS,
ffmpeg_libs_dir,
env_vars.ffmpeg_link_mode.unwrap_or(FfmpegLinkMode::Static),
env_vars.ffmpeg_link_mode.unwrap_or(FFmpegLinkMode::Static),
);
if let Some(ffmpeg_binding_path) = env_vars.ffmpeg_binding_path.as_ref() {
use_prebuilt_binding(ffmpeg_binding_path, output_binding_path);
Expand Down Expand Up @@ -574,7 +575,7 @@ fn main() {
} else if env_vars.ffmpeg_dll_path.is_some() {
dynamic_linking(env_vars);
} else {
// fallback to static linking
// fallback to normal linking
linking(env_vars);
}
}
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