add hex_to_digest and digest_to_hex

proxmox-tools/Cargo.toml

@@ -11,6 +11,7 @@ authors = [
 endian_trait = { version = "0.6", features = ["arrays"] }
 libc = "0.2"
 valgrind_request = { version = "1.1.0", optional = true }
+failure = "0.1"
 
 [features]
 default = [ "valgrind" ]

proxmox-tools/src/lib.rs

@@ -1,5 +1,7 @@
 //! This is a general utility crate used by all our rust projects.
 
+use failure::*;
+
 pub mod io;
 pub mod vec;
 
@@ -10,3 +12,44 @@ macro_rules! offsetof {
         unsafe { &(*(0 as *const $ty)).$field as *const _ as usize }
     }
 }
+
+const HEX_CHARS: &'static [u8; 16] = b"0123456789abcdef";
+
+pub fn digest_to_hex(digest: &[u8]) -> String {
+    let mut buf = Vec::<u8>::with_capacity(digest.len()*2);
+
+    for i in 0..digest.len() {
+        buf.push(HEX_CHARS[(digest[i] >> 4) as usize]);
+        buf.push(HEX_CHARS[(digest[i] & 0xf) as usize]);
+    }
+
+    unsafe { String::from_utf8_unchecked(buf) }
+}
+
+pub fn hex_to_digest(hex: &str) -> Result<[u8; 32], Error> {
+    let mut digest = [0u8; 32];
+
+    let bytes = hex.as_bytes();
+
+    if bytes.len() != 64 { bail!("got wrong digest length."); }
+
+    let val = |c| {
+        if c >= b'0' && c <= b'9' { return Ok(c - b'0'); }
+        if c >= b'a' && c <= b'f' { return Ok(c - b'a' + 10); }
+        if c >= b'A' && c <= b'F' { return Ok(c - b'A' + 10); }
+        bail!("found illegal hex character.");
+    };
+
+    let mut pos = 0;
+    for pair in bytes.chunks(2) {
+        if pos >= digest.len() { bail!("hex digest too long."); }
+        let h = val(pair[0])?;
+        let l = val(pair[1])?;
+        digest[pos] = (h<<4)|l;
+        pos +=1;
+    }
+
+    if pos != digest.len() {  bail!("hex digest too short."); }
+
+    Ok(digest)
+}