pass threadlimit down from CLIs

gitoxide-core/src/lib.rs

@@ -39,26 +39,64 @@ impl FromStr for OutputFormat {
     }
 }
 
+/// A general purpose context for many operations provided here
 pub struct Context<W1: io::Write, W2: io::Write> {
     /// If set, provide statistics to `out` in the given format
     pub output_statistics: Option<OutputFormat>,
     /// A stream to which to output operation results
     pub out: W1,
     /// A stream to which to errors
     pub err: W2,
+    /// If set, don't use more than this amount of threads.
+    /// Otherwise, usually use as many threads as there are logical cores.
+    /// A value of 0 is interpreted as no-limit
+    pub thread_limit: Option<usize>,
+}
+
+impl Default for Context<Vec<u8>, Vec<u8>> {
+    fn default() -> Self {
+        Context {
+            output_statistics: None,
+            thread_limit: None,
+            out: Vec::new(),
+            err: Vec::new(),
+        }
+    }
 }
 
 pub fn init() -> Result<()> {
     git_repository::init::repository().with_context(|| "Repository initialization failed")
 }
 
+enum EitherCache {
+    Left(pack::cache::DecodeEntryNoop),
+    Right(pack::cache::DecodeEntryLRU),
+}
+
+impl pack::cache::DecodeEntry for EitherCache {
+    fn put(&mut self, offset: u64, data: &[u8], kind: Kind, compressed_size: usize) {
+        match self {
+            EitherCache::Left(v) => v.put(offset, data, kind, compressed_size),
+            EitherCache::Right(v) => v.put(offset, data, kind, compressed_size),
+        }
+    }
+
+    fn get(&mut self, offset: u64, out: &mut Vec<u8>) -> Option<(Kind, usize)> {
+        match self {
+            EitherCache::Left(v) => v.get(offset, out),
+            EitherCache::Right(v) => v.get(offset, out),
+        }
+    }
+}
+
 pub fn verify_pack_or_pack_index<P, W1, W2>(
     path: impl AsRef<Path>,
     progress: Option<P>,
     Context {
         mut out,
         mut err,
         output_statistics,
+        thread_limit,
     }: Context<W1, W2>,
 ) -> Result<(git_object::Id, Option<index::PackFileChecksumResult>)>
 where
@@ -94,25 +132,6 @@ where
                     Err(e)
                 })
                 .ok();
-            enum EitherCache {
-                Left(pack::cache::DecodeEntryNoop),
-                Right(pack::cache::DecodeEntryLRU),
-            };
-            impl pack::cache::DecodeEntry for EitherCache {
-                fn put(&mut self, offset: u64, data: &[u8], kind: Kind, compressed_size: usize) {
-                    match self {
-                        EitherCache::Left(v) => v.put(offset, data, kind, compressed_size),
-                        EitherCache::Right(v) => v.put(offset, data, kind, compressed_size),
-                    }
-                }
-
-                fn get(&mut self, offset: u64, out: &mut Vec<u8>) -> Option<(Kind, usize)> {
-                    match self {
-                        EitherCache::Left(v) => v.get(offset, out),
-                        EitherCache::Right(v) => v.get(offset, out),
-                    }
-                }
-            }
             idx.verify_checksum_of_index(pack.as_ref(), progress, || -> EitherCache {
                 if output_statistics.is_some() {
                     // turn off acceleration as we need to see entire chains all the time

src/plumbing/lean.rs

@@ -10,6 +10,12 @@ mod options {
         /// print the program version.
         pub version: bool,
 
+        #[argh(option, short = 't')]
+        /// the amount of threads to use for some operations.
+        ///
+        /// If unset, or the value is 0, there is no limit and all logical cores can be used.
+        pub threads: Option<usize>,
+
         #[argh(subcommand)]
         pub subcommand: SubCommands,
     }
@@ -69,6 +75,7 @@ fn prepare(verbose: bool, name: &str) -> (Option<prodash::line::JoinHandle>, Opt
 pub fn main() -> Result<()> {
     pub use options::*;
     let cli: Args = crate::shared::from_env();
+    let thread_limit = cli.threads;
     match cli.subcommand {
         SubCommands::VerifyPack(VerifyPack {
             path,
@@ -85,6 +92,7 @@ pub fn main() -> Result<()> {
                     } else {
                         None
                     },
+                    thread_limit,
                     out: stdout(),
                     err: stderr(),
                 },

src/plumbing/pretty.rs

@@ -14,6 +14,12 @@ mod options {
     #[structopt(name = "gio-plumbing", about = "The git underworld")]
     #[structopt(settings = &[AppSettings::SubcommandRequired, AppSettings::ColoredHelp])]
     pub struct Args {
+        #[structopt(long, short = "t")]
+        /// The amount of threads to use for some operations.
+        ///
+        /// If unset, or the value is 0, there is no limit and all logical cores can be used.
+        pub threads: Option<usize>,
+
         #[structopt(subcommand)]
         pub cmd: Subcommands,
     }
@@ -147,6 +153,7 @@ fn prepare_and_run<T: Send + 'static>(
 
 pub fn main() -> Result<()> {
     let args = Args::from_args();
+    let thread_limit = args.threads;
     match args.cmd {
         Subcommands::VerifyPack {
             path,
@@ -165,6 +172,7 @@ pub fn main() -> Result<()> {
                     path,
                     progress,
                     core::Context {
+                        thread_limit,
                         output_statistics: if statistics { Some(format) } else { None },
                         out,
                         err,