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@xxxxxx>
---
meson.build | 5 +++-
src/lib.rs | 1 +
src/meson.build | 1 +
src/varint.rs | 92 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 98 insertions(+), 1 deletion(-)
diff --git a/meson.build b/meson.build
index 1c0e98bbc14..b52a68b0bb6 100644
--- a/meson.build
+++ b/meson.build
@@ -522,7 +522,6 @@ libgit_sources = [
'usage.c',
'userdiff.c',
'utf8.c',
- 'varint.c',
'version.c',
'versioncmp.c',
'walker.c',
@@ -1713,6 +1712,10 @@ rust_option = get_option('rust').disable_auto_if(not rust_available)
if rust_option.allowed() and meson.version().version_compare('>=1.9.0')
subdir('src')
+else
+ libgit_sources += [
+ 'varint.c',
+ ]
endif
libgit = declare_dependency(
diff --git a/src/lib.rs b/src/lib.rs
index e69de29bb2d..9da70d8b57d 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -0,0 +1 @@
+pub mod varint;
diff --git a/src/meson.build b/src/meson.build
index 2bd2045a8ab..b3164fb5ed4 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -3,6 +3,7 @@ rustmod = import('rust')
libgit_rs = static_library('git_rs',
sources: [
'lib.rs',
+ 'varint.rs',
],
rust_abi: 'c',
)
diff --git a/src/varint.rs b/src/varint.rs
new file mode 100644
index 00000000000..3d41760a555
--- /dev/null
+++ b/src/varint.rs
@@ -0,0 +1,92 @@
+use std::os::raw::c_int;
+use std::os::raw::c_uchar;
+
+#[no_mangle]
+pub unsafe extern "C" fn decode_varint(bufp: *mut *const c_uchar) -> usize {
+ let mut buf = *bufp;
+ let mut c = *buf;
+ let mut val = usize::from(c & 127);
+
+ buf = buf.add(1);
+
+ while (c & 128) != 0 {
+ val += 1;
+ if val == 0 || val.leading_zeros() < 7 {
+ return 0; // overflow
+ }
+
+ c = *buf;
+ buf = buf.add(1);
+
+ val = (val << 7) + usize::from(c & 127);
+ }
+
+ *bufp = buf;
+ val
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn encode_varint(value: usize, buf: *mut c_uchar) -> c_int {
+ let mut varint: [u8; 16] = [0; 16];
+ let mut pos = varint.len() - 1;
+
+ varint[pos] = (value & 127) as u8;
+
+ let mut value = value >> 7;
+ while value != 0 {
+ pos -= 1;
+ value -= 1;
+ varint[pos] = 128 | (value & 127) as u8;
+ value >>= 7;
+ }
+
+ if !buf.is_null() {
+ std::ptr::copy_nonoverlapping(varint.as_ptr().add(pos), buf, varint.len() - pos);
+ }
+
+ (varint.len() - pos) as c_int
+}
+
+#[cfg(test)]
+mod tests {
+ use super::*;
+
+ #[test]
+ fn test_decode_varint() {
+ unsafe {
+ assert_eq!(decode_varint(&mut [0x00].as_slice().as_ptr()), 0);
+ assert_eq!(decode_varint(&mut [0x01].as_slice().as_ptr()), 1);
+ assert_eq!(decode_varint(&mut [0x7f].as_slice().as_ptr()), 127);
+ assert_eq!(decode_varint(&mut [0x80, 0x00].as_slice().as_ptr()), 128);
+ assert_eq!(decode_varint(&mut [0x80, 0x01].as_slice().as_ptr()), 129);
+ assert_eq!(decode_varint(&mut [0x80, 0x7f].as_slice().as_ptr()), 255);
+ }
+ }
+
+ #[test]
+ fn test_encode_varint() {
+ unsafe {
+ let mut varint: [u8; 16] = [0; 16];
+
+ assert_eq!(encode_varint(0, std::ptr::null_mut()), 1);
+
+ assert_eq!(encode_varint(0, varint.as_mut_slice().as_mut_ptr()), 1);
+ assert_eq!(varint, [0; 16]);
+
+ assert_eq!(encode_varint(10, varint.as_mut_slice().as_mut_ptr()), 1);
+ assert_eq!(varint, [10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]);
+
+ assert_eq!(encode_varint(127, varint.as_mut_slice().as_mut_ptr()), 1);
+ assert_eq!(varint, [127, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]);
+
+ assert_eq!(encode_varint(128, varint.as_mut_slice().as_mut_ptr()), 2);
+ assert_eq!(varint, [128, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]);
+
+ assert_eq!(encode_varint(129, varint.as_mut_slice().as_mut_ptr()), 2);
+ assert_eq!(varint, [128, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]);
+
+ assert_eq!(encode_varint(255, varint.as_mut_slice().as_mut_ptr()), 2);
+ assert_eq!(varint, [128, 127, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]);
+ }
+ }
+}
--
2.51.0.417.g1ba7204a04.dirty
