Add util functions for bytes32 string encoding/decoding (#337)

Cargo.lock

@@ -808,6 +808,7 @@ dependencies = [
  "generic-array 0.14.4",
  "glob",
  "hex",
+ "hex-literal",
  "k256",
  "once_cell",
  "rand 0.8.4",
@@ -1174,6 +1175,12 @@ version = "0.4.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7f24254aa9a54b5c858eaee2f5bccdb46aaf0e486a595ed5fd8f86ba55232a70"
 
+[[package]]
+name = "hex-literal"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "76505e26b6ca3bbdbbb360b68472abbb80998c5fa5dc43672eca34f28258e138"
+
 [[package]]
 name = "hidapi"
 version = "1.2.6"

ethers-core/Cargo.toml

@@ -44,7 +44,7 @@ ethers = { version = "0.4.0", path = "../ethers" }
 serde_json = { version = "1.0.64", default-features = false }
 bincode = { version = "1.3.3", default-features = false }
 once_cell = { version = "1.8.0" }
-
+hex-literal = "0.3.2"
 
 [features]
 celo = [] # celo support extends the transaction format with extra fields

ethers-core/src/utils/mod.rs

@@ -36,6 +36,13 @@ pub use rlp;
 use crate::types::{Address, Bytes, U256};
 use k256::{ecdsa::SigningKey, EncodedPoint as K256PublicKey};
 use std::convert::TryInto;
+use thiserror::Error;
+
+#[derive(Debug, Error)]
+pub enum FormatBytes32StringError {
+    #[error("bytes32 strings must not exceed 32 bytes in length")]
+    TextTooLong,
+}
 
 /// 1 Ether = 1e18 Wei == 0x0de0b6b3a7640000 Wei
 pub const WEI_IN_ETHER: U256 = U256([0x0de0b6b3a7640000, 0x0, 0x0, 0x0]);
@@ -156,6 +163,30 @@ pub fn to_checksum(addr: &Address, chain_id: Option<u8>) -> String {
         })
 }
 
+/// Returns a bytes32 string representation of text. If the length of text exceeds 32 bytes,
+/// an error is returned.
+pub fn format_bytes32_string(text: &str) -> Result<[u8; 32], FormatBytes32StringError> {
+    let str_bytes: &[u8] = text.as_bytes();
+    if str_bytes.len() > 32 {
+        return Err(FormatBytes32StringError::TextTooLong);
+    }
+
+    let mut bytes32: [u8; 32] = [0u8; 32];
+    bytes32[..str_bytes.len()].copy_from_slice(str_bytes);
+
+    Ok(bytes32)
+}
+
+/// Returns the decoded string represented by the bytes32 encoded data.
+pub fn parse_bytes32_string(bytes: &[u8; 32]) -> Result<&str, std::str::Utf8Error> {
+    let mut length = 0;
+    while length < 32 && bytes[length] != 0 {
+        length += 1;
+    }
+
+    std::str::from_utf8(&bytes[..length])
+}
+
 /// A bit of hack to find an unused TCP port.
 ///
 /// Does not guarantee that the given port is unused after the function exists, just that it was
@@ -173,6 +204,7 @@ pub(crate) fn unused_port() -> u16 {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use hex_literal::hex;
 
     #[test]
     fn wei_in_ether() {
@@ -359,4 +391,64 @@ mod tests {
             assert_eq!(expected, get_create2_address(from, salt, init_code))
         }
     }
+
+    #[test]
+    fn bytes32_string_parsing() {
+        let text_bytes_list = vec![
+            (
+                "",
+                hex!("0000000000000000000000000000000000000000000000000000000000000000"),
+            ),
+            (
+                "A",
+                hex!("4100000000000000000000000000000000000000000000000000000000000000"),
+            ),
+            (
+                "ABCDEFGHIJKLMNOPQRSTUVWXYZ012345",
+                hex!("4142434445464748494a4b4c4d4e4f505152535455565758595a303132333435"),
+            ),
+            (
+                "!@#$%^&*(),./;'[]",
+                hex!("21402324255e262a28292c2e2f3b275b5d000000000000000000000000000000"),
+            ),
+        ];
+
+        for (text, bytes) in text_bytes_list {
+            assert_eq!(text, parse_bytes32_string(&bytes).unwrap());
+        }
+    }
+
+    #[test]
+    fn bytes32_string_formatting() {
+        let text_bytes_list = vec![
+            (
+                "",
+                hex!("0000000000000000000000000000000000000000000000000000000000000000"),
+            ),
+            (
+                "A",
+                hex!("4100000000000000000000000000000000000000000000000000000000000000"),
+            ),
+            (
+                "ABCDEFGHIJKLMNOPQRSTUVWXYZ012345",
+                hex!("4142434445464748494a4b4c4d4e4f505152535455565758595a303132333435"),
+            ),
+            (
+                "!@#$%^&*(),./;'[]",
+                hex!("21402324255e262a28292c2e2f3b275b5d000000000000000000000000000000"),
+            ),
+        ];
+
+        for (text, bytes) in text_bytes_list {
+            assert_eq!(bytes, format_bytes32_string(text).unwrap());
+        }
+    }
+
+    #[test]
+    fn bytes32_string_formatting_too_long() {
+        assert!(matches!(
+            format_bytes32_string("ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456").unwrap_err(),
+            FormatBytes32StringError::TextTooLong
+        ));
+    }
 }