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std.RingBuffer: use sliceAt/sliceFirst in read*AssumeLength

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dweiller 2024-03-10 18:17:23 +11:00
parent d942096a44
commit 6fe2b40778
1 changed files with 14 additions and 13 deletions
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27
lib/std/RingBuffer.zig
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@ -150,12 +150,8 @@ pub fn readFirst(self: *RingBuffer, dest: []u8, length: usize) Error!void {
/// Uses memcpy and so `dest` must not overlap ring buffer data. /// Uses memcpy and so `dest` must not overlap ring buffer data.
pub fn readFirstAssumeLength(self: *RingBuffer, dest: []u8, length: usize) void { pub fn readFirstAssumeLength(self: *RingBuffer, dest: []u8, length: usize) void {
assert(length <= self.len() and length <= dest.len); assert(length <= self.len() and length <= dest.len);
const data_start = self.mask(self.read_index); const slice = self.sliceAt(self.read_index, length);
const part1_data_end = @min(self.data.len, data_start + length); slice.copyTo(dest);
const part1_len = part1_data_end - data_start;
const part2_len = length - part1_len;
@memcpy(dest[0..part1_len], self.data[data_start..part1_data_end]);
@memcpy(dest[part1_len..length], self.data[0..part2_len]);
self.read_index = self.mask2(self.read_index + length); self.read_index = self.mask2(self.read_index + length);
} }
@ -174,13 +170,12 @@ pub fn readLast(self: *RingBuffer, dest: []u8, length: usize) Error!void {
/// Reduces write index by `length`. /// Reduces write index by `length`.
pub fn readLastAssumeLength(self: *RingBuffer, dest: []u8, length: usize) void { pub fn readLastAssumeLength(self: *RingBuffer, dest: []u8, length: usize) void {
assert(length <= self.len() and length <= dest.len); assert(length <= self.len() and length <= dest.len);
const data_start = self.mask(self.write_index + self.data.len - length); const slice = self.sliceLast(length);
const part1_data_end = @min(self.data.len, data_start + length); slice.copyTo(dest);
const part1_len = part1_data_end - data_start; self.write_index = if (self.write_index >= self.data.len)
const part2_len = length - part1_len; self.write_index - length
@memcpy(dest[0..part1_len], self.data[data_start..part1_data_end]); else
@memcpy(dest[part1_len..length], self.data[0..part2_len]); self.mask(self.write_index + self.data.len - length);
self.write_index = if (self.write_index >= self.data.len) self.write_index - length else data_start;
} }
/// Returns `true` if the ring buffer is empty and `false` otherwise. /// Returns `true` if the ring buffer is empty and `false` otherwise.
@ -206,6 +201,12 @@ pub fn len(self: RingBuffer) usize {
pub const Slice = struct { pub const Slice = struct {
first: []u8, first: []u8,
second: []u8, second: []u8,
/// Copy data from `self` into `dest`
pub fn copyTo(self: Slice, dest: []u8) void {
@memcpy(dest[0..self.first.len], self.first);
@memcpy(dest[self.first.len..][0..self.second.len], self.second);
}
}; };
/// Returns a `Slice` for the region of the ring buffer starting at /// Returns a `Slice` for the region of the ring buffer starting at