Read all mandatory and optional chunks (#279)

git-chunk/src/lib.rs

@@ -17,6 +17,31 @@ pub mod file {
         use crate::file::Index;
         use std::ops::Range;
 
+        ///
+        pub mod not_found {
+            use std::fmt::{Display, Formatter};
+
+            /// The error returned by [Index::offset_by_kind()][super::Index::offset_by_kind()].
+            #[allow(missing_docs)]
+            #[derive(Debug)]
+            pub struct Error {
+                pub kind: crate::Kind,
+                pub name: &'static str,
+            }
+
+            impl Display for Error {
+                fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+                    write!(
+                        f,
+                        "Chunk named {:?} (id = {}) was not found in chunk file index",
+                        self.name, self.kind
+                    )
+                }
+            }
+
+            impl std::error::Error for Error {}
+        }
+
         /// An entry of a chunk file index
         pub struct Entry {
             /// The kind of the chunk file
@@ -32,10 +57,15 @@ pub mod file {
             pub const EMPTY_SIZE: usize = Index::ENTRY_SIZE;
 
             /// Find a chunk of `kind` and return its offset into the data if found
-            pub fn offset_by_kind(&self, kind: crate::Kind) -> Option<Range<crate::file::Offset>> {
+            pub fn offset_by_kind(
+                &self,
+                kind: crate::Kind,
+                name: &'static str,
+            ) -> Result<Range<crate::file::Offset>, not_found::Error> {
                 self.chunks
                     .iter()
                     .find_map(|c| (c.kind == kind).then(|| c.offset.clone()))
+                    .ok_or_else(|| not_found::Error { kind, name })
             }
         }
     }

git-pack/src/multi_index.rs

@@ -1,5 +1,7 @@
 #![allow(missing_docs, unused)]
+
 use filebuffer::FileBuffer;
+use std::ops::Range;
 
 /// Known multi-index file versions
 #[derive(PartialEq, Eq, Ord, PartialOrd, Debug, Hash, Clone, Copy)]
@@ -25,6 +27,7 @@ pub struct File {
     num_chunks: u8,
     /// The amount of pack files contained within
     num_packs: u32,
+    fanout: Range<git_chunk::file::Offset>,
 }
 
 ///
@@ -41,9 +44,27 @@ pub mod access {
     }
 }
 
+mod chunk {
+    pub mod pack_names {
+        pub const ID: git_chunk::Kind = 0x504e414d; /* "PNAM" */
+    }
+    pub mod fanout {
+        pub const ID: git_chunk::Kind = 0x4f494446; /* "OIDF" */
+    }
+    pub mod lookup {
+        pub const ID: git_chunk::Kind = 0x4f49444c; /* "OIDL" */
+    }
+    pub mod offsets {
+        pub const ID: git_chunk::Kind = 0x4f4f4646; /* "OOFF" */
+    }
+    pub mod large_offsets {
+        pub const ID: git_chunk::Kind = 0x4c4f4646; /* "LOFF" */
+    }
+}
+
 ///
 pub mod init {
-    use crate::multi_index::{File, Version};
+    use crate::multi_index::{chunk, File, Version};
     use byteorder::{BigEndian, ByteOrder, ReadBytesExt};
     use filebuffer::FileBuffer;
     use std::convert::{TryFrom, TryInto};
@@ -65,6 +86,8 @@ pub mod init {
             UnsupportedHashKind { kind: u8 },
             #[error(transparent)]
             ChunkFileDecode(#[from] git_chunk::file::decode::Error),
+            #[error(transparent)]
+            MissingChunk(#[from] git_chunk::file::index::not_found::Error),
         }
     }
     pub use error::Error;
@@ -128,12 +151,18 @@ pub mod init {
             };
 
             let chunks = git_chunk::file::Index::from_bytes(&data, HEADER_LEN, num_chunks as u32)?;
+            let pack_names = chunks.offset_by_kind(chunk::pack_names::ID, "PNAM")?;
+            let fanout = chunks.offset_by_kind(chunk::fanout::ID, "OIDF")?;
+            let lookup = chunks.offset_by_kind(chunk::lookup::ID, "OIDL")?;
+            let offsets = chunks.offset_by_kind(chunk::offsets::ID, "OOFF")?;
+            let large_offsets = chunks.offset_by_kind(chunk::large_offsets::ID, "LOFF").ok();
 
             Ok(File {
                 data,
                 path: path.to_owned(),
                 version,
                 hash_kind,
+                fanout,
                 num_chunks,
                 num_packs,
             })