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Move base64 and tests to b64 module

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This commit is contained in:
Eryn Wells 2018-03-25 16:42:25 -04:00
parent feaedd8194
commit 36e06e5570
2 changed files with 92 additions and 91 deletions
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91
src/b64.rs Normal file
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@ -0,0 +1,91 @@
static B64: &'static str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+\\";
pub fn base64(hex: &str) -> Result<String, String> {
let mut out = String::from("");
let mut num_bits = 0;
let mut acc: u32 = 0;
for (idx, c) in hex.char_indices() {
if let Some(c_digit) = c.to_digit(16) {
// Accumulate bytes until we have 6 chunks of 4.
acc = (acc << 4) + c_digit;
num_bits += 4;
if idx % 6 != 5 {
continue;
}
// Read out 4 chunks of 6.
for i in (0..4).rev() {
let out_char_idx = ((acc >> (6 * i)) & 0x3F) as usize;
// TODO: I don't like this nth() call.
if let Some(out_char) = B64.chars().nth(out_char_idx) {
out.push(out_char);
} else {
return Err(format!("Couldn't make output char from {}", out_char_idx));
}
}
acc = 0;
num_bits = 0;
} else {
return Err(format!("Invalid input: {}", c));
}
}
if acc != 0 {
// Pad the string if we have bits remaining.
acc = acc << (24 - num_bits);
let padding = (24 - num_bits) / 6;
for i in (0..4).rev() {
let out_char_idx = ((acc >> (6 * i)) & 0x3F) as usize;
if i < padding {
out.push('=');
} else if let Some(out_char) = B64.chars().nth(out_char_idx) {
out.push(out_char);
} else {
return Err(format!("Couldn't make output char from {}", out_char_idx));
}
}
}
Ok(out)
}
#[cfg(test)]
mod tests {
use super::base64;
#[test]
fn small_wikipedia_example() {
let input = "4d616e";
let ex_output = "TWFu";
println!("");
let output = base64(input).expect("Error converting to base64");
assert_eq!(output, ex_output);
}
#[test]
fn one_byte_padding() {
let input = "6f6d";
let ex_output = "b20=";
println!("");
let output = base64(input).expect("Error converting to base64");
assert_eq!(output, ex_output);
}
#[test]
fn two_byte_padding() {
let input = "6f";
let ex_output = "bw==";
println!("");
let output = base64(input).expect("Error converting to base64");
assert_eq!(output, ex_output);
}
#[test]
fn cryptopals_input() {
let input = "49276d206b696c6c696e6720796f757220627261696e206c696b65206120706f69736f6e6f7573206d757368726f6f6d";
let ex_output = "SSdtIGtpbGxpbmcgeW91ciBicmFpbiBsaWtlIGEgcG9pc29ub3VzIG11c2hyb29t";
println!("");
let output = base64(input).expect("Error converting to base64");
assert_eq!(output, ex_output);
}
}

92
src/lib.rs
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@ -1,91 +1 @@
static B64: &'static str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+\\";
pub fn base64(hex: &str) -> Result<String, String> {
let mut out = String::from("");
let mut num_bits = 0;
let mut acc: u32 = 0;
for (idx, c) in hex.char_indices() {
if let Some(c_digit) = c.to_digit(16) {
// Accumulate bytes until we have 6 chunks of 4.
acc = (acc << 4) + c_digit;
num_bits += 4;
if idx % 6 != 5 {
continue;
}
// Read out 4 chunks of 6.
for i in (0..4).rev() {
let out_char_idx = ((acc >> (6 * i)) & 0x3F) as usize;
// TODO: I don't like this nth() call.
if let Some(out_char) = B64.chars().nth(out_char_idx) {
out.push(out_char);
} else {
return Err(format!("Couldn't make output char from {}", out_char_idx));
}
}
acc = 0;
num_bits = 0;
} else {
return Err(format!("Invalid input: {}", c));
}
}
if acc != 0 {
// Pad the string if we have bits remaining.
acc = acc << (24 - num_bits);
let padding = (24 - num_bits) / 6;
for i in (0..4).rev() {
let out_char_idx = ((acc >> (6 * i)) & 0x3F) as usize;
if i < padding {
out.push('=');
} else if let Some(out_char) = B64.chars().nth(out_char_idx) {
out.push(out_char);
} else {
return Err(format!("Couldn't make output char from {}", out_char_idx));
}
}
}
Ok(out)
}
#[cfg(test)]
mod tests {
use super::base64;
#[test]
fn small_wikipedia_example() {
let input = "4d616e";
let ex_output = "TWFu";
println!("");
let output = base64(input).expect("Error converting to base64");
assert_eq!(output, ex_output);
}
#[test]
fn one_byte_padding() {
let input = "6f6d";
let ex_output = "b20=";
println!("");
let output = base64(input).expect("Error converting to base64");
assert_eq!(output, ex_output);
}
#[test]
fn two_byte_padding() {
let input = "6f";
let ex_output = "bw==";
println!("");
let output = base64(input).expect("Error converting to base64");
assert_eq!(output, ex_output);
}
#[test]
fn cryptopals_input() {
let input = "49276d206b696c6c696e6720796f757220627261696e206c696b65206120706f69736f6e6f7573206d757368726f6f6d";
let ex_output = "SSdtIGtpbGxpbmcgeW91ciBicmFpbiBsaWtlIGEgcG9pc29ub3VzIG11c2hyb29t";
println!("");
let output = base64(input).expect("Error converting to base64");
assert_eq!(output, ex_output);
}
}
pub mod b64;