From 60dcd4ca4f929bfd850a15f28fddac3d5e99192d Mon Sep 17 00:00:00 2001
From: mriise <me@mriise.net>
Date: Tue, 12 Jul 2022 18:37:06 +0000
Subject: [PATCH] implement stack-based display and multibase encoding

---
 Cargo.toml |  6 ++---
 src/cid.rs | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/lib.rs |  1 -
 3 files changed, 73 insertions(+), 4 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index f5ff23a..dddcdb1 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -10,9 +10,9 @@ readme = "README.md"
 edition = "2018"
 
 [features]
-default = ["std", "multihash/default"]
+default = [ "multibase"]
 std = ["multihash/std", "unsigned-varint/std", "alloc", "multibase/std"]
-alloc = ["multibase", "multihash/alloc", "core2/alloc", "serde/alloc"]
+alloc = ["multibase/alloc", "multihash/alloc", "core2/alloc", "serde/alloc"]
 arb = ["quickcheck", "rand", "multihash/arb", "multihash/sha2", "arbitrary"]
 scale-codec = ["parity-scale-codec", "multihash/scale-codec"]
 serde-codec = ["alloc", "serde", "multihash/serde-codec", "serde_bytes"]
@@ -21,7 +21,7 @@ serde-codec = ["alloc", "serde", "multihash/serde-codec", "serde_bytes"]
 multihash = { version = "0.16.2", default-features = false }
 unsigned-varint = { version = "0.7.0", default-features = false }
 
-multibase = { version = "0.9.1", optional = true, default-features = false }
+multibase = { version = "0.9.1", optional = true, default-features = false, git = "https://github.com/mriise/rust-multibase", branch = "stack" }
 parity-scale-codec = { version = "3.0.0", default-features = false, features = ["derive"], optional = true }
 quickcheck = { version = "0.9.2", optional = true }
 rand = { version = "0.7.3", optional = true }
diff --git a/src/cid.rs b/src/cid.rs
index d6a852f..027abb0 100644
--- a/src/cid.rs
+++ b/src/cid.rs
@@ -7,6 +7,7 @@
 //! import the `Cid` type from this module.
 use core::convert::TryFrom;
 
+use multibase::{StackBase, StackVec, StackString};
 #[cfg(feature = "alloc")]
 use multibase::{encode as base_encode, Base};
 
@@ -182,6 +183,26 @@ impl<const S: usize> Cid<S> {
         multibase::encode(Base::Base32Lower, self.to_bytes().as_slice())
     }
 
+    fn to_stack_string_v0<const STR: usize>(&self) -> StackString<STR> { 
+        let mut vec = StackVec::<u8, STR>::default();
+        {
+            let buf: &mut [u8] = &mut vec;
+            // unwraps because it assumes const was written to be generic over base + CID and thus should be correctly sized
+            self.hash.write(buf).unwrap();
+        }
+        StackBase::<0, STR>::Base58BtcS.encode(vec).unwrap()
+    }
+
+    fn to_stack_string_v1<const STR: usize>(&self) -> StackString<STR> { 
+        let mut vec = StackVec::<u8, STR>::default();
+        {
+            let buf: &mut [u8] = &mut vec;
+            // unwraps because it assumes const was written to be generic over base + CID and thus should be correctly sized
+            self.write_bytes_v1(buf).unwrap();
+        }
+        StackBase::<0, STR>::Base32Lower.encode(vec).unwrap()
+    }
+
     /// Convert CID into a multibase encoded string
     ///
     /// # Example
@@ -222,6 +243,55 @@ impl<const S: usize> Default for Cid<S> {
     }
 }
 
+#[cfg(not(feature = "alloc"))]
+/// takes a numerator of a fraction (magic number!)
+/// and the input size to calculate the expected output size
+/// 
+/// adds the buffer sizes of varint
+/// 
+/// 58: 136566
+/// 10: 240824
+const fn encoded_size(size: usize, num: usize) -> usize {
+    let version_size = 1;
+    let codec_size = 4;
+    (size * num / 100000) + 1 + version_size + codec_size
+}
+
+#[cfg(not(feature = "alloc"))]
+macro_rules! stack_display {
+    ($($size:literal,)*) => {
+        $(
+            impl core::fmt::Display for Cid<$size> {
+                fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
+            
+                    match self.version {
+                        Version::V0 => write!(f, "{}", self.to_stack_string_v0::<{encoded_size($size, 136566)}>()),
+                        Version::V1 =>  write!(f, "{}", self.to_stack_string_v1::<{encoded_size($size, 240824)}>()),
+                    }
+                }
+            }
+
+            impl core::fmt::Debug for Cid<$size> {
+                fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+                    if f.alternate() {
+                        f.debug_struct("Cid")
+                            .field("version", &self.version())
+                            .field("codec", &self.codec())
+                            .field("hash", self.hash())
+                            .finish()
+                    } else {
+                        write!(f, "Cid({})", self)
+                    }
+                }
+            }
+    
+        )*
+    };
+}
+
+#[cfg(not(feature = "alloc"))]
+stack_display!(32, 64, 128, 256, 512, 1024, 2048,);
+
 // TODO: remove the dependency on alloc by fixing
 // https://github.com/multiformats/rust-multibase/issues/33
 #[cfg(feature = "alloc")]
diff --git a/src/lib.rs b/src/lib.rs
index ee839d1..1f72c89 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -18,7 +18,6 @@ pub use self::cid::Cid as CidGeneric;
 pub use self::error::{Error, Result};
 pub use self::version::Version;
 
-#[cfg(feature = "alloc")]
 pub use multibase;
 pub use multihash;