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std.zig.ErrorBundle: add special representation for empty

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This allows the common case of no compilation errors to be represented
without any allocations.
This commit is contained in:
Andrew Kelley 2023-02-28 16:36:09 -07:00
parent 6d88c3e935
commit a42888e145
1 changed files with 22 additions and 0 deletions
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22
lib/std/zig/ErrorBundle.zig
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@ -2,11 +2,21 @@
//! so that they can be created and destroyed appropriately. This structure
//! is used to collect all the errors from the various places into one
//! convenient place for API users to consume.
//!
//! There is one special encoding for this data structure. If both arrays are
//! empty, it means there are no errors. This special encoding exists so that
//! heap allocation is not needed in the common case of no errors.
string_bytes: []const u8,
/// The first thing in this array is an `ErrorMessageList`.
extra: []const u32,
/// Special encoding when there are no errors.
pub const empty: ErrorBundle = .{
.string_bytes = &.{},
.extra = &.{},
};
// An index into `extra` pointing at an `ErrorMessage`.
pub const MessageIndex = enum(u32) {
_,
@ -72,6 +82,7 @@ pub fn deinit(eb: *ErrorBundle, gpa: Allocator) void {
}
pub fn errorMessageCount(eb: ErrorBundle) u32 {
if (eb.extra.len == 0) return 0;
return eb.getErrorMessageList().len;
}
@ -313,6 +324,17 @@ pub const Wip = struct {
pub fn toOwnedBundle(wip: *Wip) !ErrorBundle {
const gpa = wip.gpa;
if (wip.root_list.items.len == 0) {
// Special encoding when there are no errors.
wip.deinit();
wip.* = .{
.gpa = gpa,
.string_bytes = .{},
.extra = .{},
.root_list = .{},
};
return empty;
}
wip.setExtra(0, ErrorMessageList{
.len = @intCast(u32, wip.root_list.items.len),
.start = @intCast(u32, wip.extra.items.len),