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Merge pull request #19238 from dweiller/ring-buffer

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std.RingBuffer: minor cleanup and doc improvements
This commit is contained in:
Andrew Kelley
2024-03-11 18:49:16 -07:00
committed by GitHub
parent cb4e087fda 6fe2b40778
commit da5b16f9e2
1 changed files with 19 additions and 14 deletions
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33
lib/std/RingBuffer.zig
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@@ -74,6 +74,7 @@ pub fn writeSlice(self: *RingBuffer, bytes: []const u8) Error!void {
/// bytes will be overwritten.
/// Uses memcpy and so `bytes` must not overlap ring buffer data.
pub fn writeSliceAssumeCapacity(self: *RingBuffer, bytes: []const u8) void {
assert(bytes.len <= self.data.len);
const data_start = self.mask(self.write_index);
const part1_data_end = @min(data_start + bytes.len, self.data.len);
const part1_len = part1_data_end - data_start;
@@ -104,6 +105,7 @@ pub fn writeSliceForwards(self: *RingBuffer, bytes: []const u8) Error!void {
/// bytes will be overwritten.
/// Uses copyForwards and can write slices from this RingBuffer into itself.
pub fn writeSliceForwardsAssumeCapacity(self: *RingBuffer, bytes: []const u8) void {
assert(bytes.len <= self.data.len);
const data_start = self.mask(self.write_index);
const part1_data_end = @min(data_start + bytes.len, self.data.len);
const part1_len = part1_data_end - data_start;
@@ -148,18 +150,15 @@ pub fn readFirst(self: *RingBuffer, dest: []u8, length: usize) Error!void {
/// Uses memcpy and so `dest` must not overlap ring buffer data.
pub fn readFirstAssumeLength(self: *RingBuffer, dest: []u8, length: usize) void {
assert(length <= self.len() and length <= dest.len);
const data_start = self.mask(self.read_index);
const part1_data_end = @min(self.data.len, data_start + length);
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]);
const slice = self.sliceAt(self.read_index, length);
slice.copyTo(dest);
self.read_index = self.mask2(self.read_index + length);
}
/// Reads last `length` bytes written to the ring buffer into `dest`; Returns
/// Error.ReadLengthInvalid if length greater than ring or dest length
/// Uses memcpy and so `dest` must not overlap ring buffer data.
/// Reduces write index by `length`.
pub fn readLast(self: *RingBuffer, dest: []u8, length: usize) Error!void {
if (length > self.len() or length > dest.len) return error.ReadLengthInvalid;
self.readLastAssumeLength(dest, length);
@@ -168,15 +167,15 @@ pub fn readLast(self: *RingBuffer, dest: []u8, length: usize) Error!void {
/// Reads last `length` bytes written to the ring buffer into `dest`;
/// Asserts that length not greater than ring buffer or dest length
/// Uses memcpy and so `dest` must not overlap ring buffer data.
/// Reduces write index by `length`.
pub fn readLastAssumeLength(self: *RingBuffer, dest: []u8, length: usize) void {
assert(length <= self.len() and length <= dest.len);
const data_start = self.mask(self.write_index + self.data.len - length);
const part1_data_end = @min(self.data.len, data_start + length);
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.write_index = if (self.write_index >= self.data.len) self.write_index - length else data_start;
const slice = self.sliceLast(length);
slice.copyTo(dest);
self.write_index = if (self.write_index >= self.data.len)
self.write_index - length
else
self.mask(self.write_index + self.data.len - length);
}
/// Returns `true` if the ring buffer is empty and `false` otherwise.
@@ -189,7 +188,7 @@ pub fn isFull(self: RingBuffer) bool {
return self.mask2(self.write_index + self.data.len) == self.read_index;
}
/// Returns the length
/// Returns the length of data available for reading
pub fn len(self: RingBuffer) usize {
const wrap_offset = 2 * self.data.len * @intFromBool(self.write_index < self.read_index);
const adjusted_write_index = self.write_index + wrap_offset;
@@ -202,6 +201,12 @@ pub fn len(self: RingBuffer) usize {
pub const Slice = struct {
first: []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