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8832e728d3
Implement a trivial test balloon for our Rust build infrastructure by reimplementing the "varint.c" subsystem in Rust. This subsystem is chosen because it is trivial to convert and because it doesn't have any dependencies to other components of Git. If support for Rust is enabled, we stop compiling "varint.c" and instead compile and use "src/varint.rs". Signed-off-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Junio C Hamano <gitster@pobox.com>
93 lines
2.8 KiB
Rust
93 lines
2.8 KiB
Rust
#[no_mangle]
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pub unsafe extern "C" fn decode_varint(bufp: *mut *const u8) -> u64 {
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let mut buf = *bufp;
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let mut c = *buf;
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let mut val = u64::from(c & 127);
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buf = buf.add(1);
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while (c & 128) != 0 {
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val = val.wrapping_add(1);
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if val == 0 || val.leading_zeros() < 7 {
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return 0; // overflow
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}
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c = *buf;
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buf = buf.add(1);
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val = (val << 7) + u64::from(c & 127);
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}
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*bufp = buf;
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val
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}
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#[no_mangle]
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pub unsafe extern "C" fn encode_varint(value: u64, buf: *mut u8) -> u8 {
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let mut varint: [u8; 16] = [0; 16];
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let mut pos = varint.len() - 1;
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varint[pos] = (value & 127) as u8;
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let mut value = value >> 7;
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while value != 0 {
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pos -= 1;
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value -= 1;
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varint[pos] = 128 | (value & 127) as u8;
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value >>= 7;
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}
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if !buf.is_null() {
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std::ptr::copy_nonoverlapping(varint.as_ptr().add(pos), buf, varint.len() - pos);
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}
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(varint.len() - pos) as u8
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn test_decode_varint() {
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unsafe {
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assert_eq!(decode_varint(&mut [0x00].as_slice().as_ptr()), 0);
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assert_eq!(decode_varint(&mut [0x01].as_slice().as_ptr()), 1);
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assert_eq!(decode_varint(&mut [0x7f].as_slice().as_ptr()), 127);
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assert_eq!(decode_varint(&mut [0x80, 0x00].as_slice().as_ptr()), 128);
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assert_eq!(decode_varint(&mut [0x80, 0x01].as_slice().as_ptr()), 129);
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assert_eq!(decode_varint(&mut [0x80, 0x7f].as_slice().as_ptr()), 255);
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// Overflows are expected to return 0.
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assert_eq!(decode_varint(&mut [0x88; 16].as_slice().as_ptr()), 0);
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}
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}
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#[test]
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fn test_encode_varint() {
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unsafe {
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let mut varint: [u8; 16] = [0; 16];
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assert_eq!(encode_varint(0, std::ptr::null_mut()), 1);
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assert_eq!(encode_varint(0, varint.as_mut_slice().as_mut_ptr()), 1);
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assert_eq!(varint, [0; 16]);
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assert_eq!(encode_varint(10, varint.as_mut_slice().as_mut_ptr()), 1);
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assert_eq!(varint, [10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]);
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assert_eq!(encode_varint(127, varint.as_mut_slice().as_mut_ptr()), 1);
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assert_eq!(varint, [127, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]);
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assert_eq!(encode_varint(128, varint.as_mut_slice().as_mut_ptr()), 2);
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assert_eq!(varint, [128, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]);
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assert_eq!(encode_varint(129, varint.as_mut_slice().as_mut_ptr()), 2);
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assert_eq!(varint, [128, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]);
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assert_eq!(encode_varint(255, varint.as_mut_slice().as_mut_ptr()), 2);
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assert_eq!(varint, [128, 127, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]);
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}
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}
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}
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