feat: remove new_from_prefix() method

Credit goes to @dvc94ch as this code is based on
#18

The code to generate a CID from a prefix is not part of Rust IPFS Bitswap:
https://github.com/ipfs-rust/rust-ipfs/blob/d9955928bb05d07523e4955bc247e49b670f0c48/bitswap/src/prefix.rs

BREAKING CHANGE: `Cid::new_from_prefix()` was removed

Use `Cid::new_v0()` or `Cid::new_v1()` instead.

src/arb.rs

@@ -5,7 +5,7 @@ use quickcheck::{Arbitrary, Gen};
 use rand::seq::SliceRandom;
 use rand::Rng;
 
-use crate::{Cid, Codec, Prefix, Version};
+use crate::{Cid, Codec, Version};
 
 const CODECS: [Codec; 18] = [
     Codec::Raw,
@@ -67,15 +67,3 @@ impl Arbitrary for Cid {
         }
     }
 }
-
-impl Arbitrary for Prefix {
-    fn arbitrary<G: Gen>(g: &mut G) -> Self {
-        let cid: Cid = Arbitrary::arbitrary(g);
-        Prefix {
-            version: cid.version(),
-            codec: cid.codec(),
-            mh_type: cid.hash().algorithm(),
-            mh_len: cid.hash().digest().len(),
-        }
-    }
-}

src/cid.rs

@@ -6,7 +6,6 @@ use unsigned_varint::{decode as varint_decode, encode as varint_encode};
 
 use crate::codec::Codec;
 use crate::error::{Error, Result};
-use crate::prefix::Prefix;
 use crate::version::Version;
 
 /// Representation of a CID.
@@ -55,19 +54,6 @@ impl Cid {
         }
     }
 
-    /// Create a new CID from a prefix and some data.
-    pub fn new_from_prefix(prefix: &Prefix, data: &[u8]) -> Cid {
-        let mut hash = prefix.mh_type.hasher().unwrap().digest(data);
-        if prefix.mh_len < hash.digest().len() {
-            hash = multihash::wrap(hash.algorithm(), &hash.digest()[..prefix.mh_len]);
-        }
-        Cid {
-            version: prefix.version,
-            codec: prefix.codec,
-            hash,
-        }
-    }
-
     /// Returns the cid version.
     pub fn version(&self) -> Version {
         self.version
@@ -116,16 +102,6 @@ impl Cid {
             Version::V1 => self.to_bytes_v1(),
         }
     }
-
-    /// Return the prefix of the CID.
-    pub fn prefix(&self) -> Prefix {
-        Prefix {
-            version: self.version,
-            codec: self.codec,
-            mh_type: self.hash.algorithm(),
-            mh_len: self.hash.digest().len(),
-        }
-    }
 }
 
 #[allow(clippy::derive_hash_xor_eq)]

src/lib.rs

@@ -7,7 +7,6 @@
 mod cid;
 mod codec;
 mod error;
-mod prefix;
 mod version;
 
 #[cfg(any(test, feature = "test"))]
@@ -16,5 +15,4 @@ mod arb;
 pub use self::cid::Cid;
 pub use self::codec::Codec;
 pub use self::error::{Error, Result};
-pub use self::prefix::Prefix;
 pub use self::version::Version;

tests/lib.rs

@@ -2,7 +2,7 @@ use std::collections::HashMap;
 use std::convert::{TryFrom, TryInto};
 use std::str::FromStr;
 
-use cid::{Cid, Codec, Error, Prefix, Version};
+use cid::{Cid, Codec, Error, Version};
 use multihash::Sha2_256;
 
 #[test]
@@ -57,24 +57,6 @@ fn v0_error() {
     assert_eq!(Cid::try_from(bad), Err(Error::ParsingError));
 }
 
-#[test]
-fn prefix_roundtrip() {
-    let data = b"awesome test content";
-    let h = Sha2_256::digest(data);
-
-    let cid = Cid::new_v1(Codec::DagProtobuf, h);
-    let prefix = cid.prefix();
-
-    let cid2 = Cid::new_from_prefix(&prefix, data);
-
-    assert_eq!(cid, cid2);
-
-    let prefix_bytes = prefix.as_bytes();
-    let prefix2 = Prefix::new_from_bytes(&prefix_bytes).unwrap();
-
-    assert_eq!(prefix, prefix2);
-}
-
 #[test]
 fn from() {
     let the_hash = "QmdfTbBqBPQ7VNxZEYEj14VmRuZBkqFbiwReogJgS1zR1n";
@@ -95,14 +77,9 @@ fn from() {
 #[test]
 fn test_hash() {
     let data: Vec<u8> = vec![1, 2, 3];
-    let prefix = Prefix {
-        version: Version::V0,
-        codec: Codec::DagProtobuf,
-        mh_type: multihash::Code::Sha2_256,
-        mh_len: 32,
-    };
+    let hash = Sha2_256::digest(&data);
     let mut map = HashMap::new();
-    let cid = Cid::new_from_prefix(&prefix, &data);
+    let cid = Cid::new_v0(hash).unwrap();
     map.insert(cid.clone(), data.clone());
     assert_eq!(&data, map.get(&cid).unwrap());
 }