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Fix edge-case memory bug in StringTable #1430

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Fix edge-case memory bug in StringTable #1430

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20 changes: 13 additions & 7 deletions src/StringTable.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -19,7 +19,7 @@ pub const Index = u32;

/// Returns the index of a string key, if it exists
/// complexity: hashmap lookup
pub fn index(table: *StringTable, key: []const u8) ?Index {
pub fn index(table: *const StringTable, key: []const u8) ?Index {
const slice_context: SliceAdapter = .{ .string_bytes = &table.string_bytes };
const found_entry = table.string_table.getEntryAdapted(key, slice_context);
if (found_entry) |e| return e.key_ptr.*;
Expand All @@ -28,21 +28,27 @@ pub fn index(table: *StringTable, key: []const u8) ?Index {

/// Returns the index of a string key, inserting if not exists
/// complexity: hashmap lookup / update
pub fn indexOrPut(table: *StringTable, allocator: std.mem.Allocator, key: []const u8) !Index {
///
/// Assumes `key` does not contain any zero bytes
pub fn indexOrPut(table: *StringTable, allocator: std.mem.Allocator, key: []const u8) error{OutOfMemory}!Index {
const slice_context: SliceAdapter = .{ .string_bytes = &table.string_bytes };
const index_context: IndexContext = .{ .string_bytes = &table.string_bytes };
const entry = try table.string_table.getOrPutContextAdapted(allocator, key, slice_context, index_context);
if (!entry.found_existing) {
entry.key_ptr.* = @intCast(table.string_bytes.items.len);
try table.string_bytes.appendSlice(allocator, key);
try table.string_bytes.append(allocator, '\x00');
errdefer table.string_table.removeByPtr(entry.key_ptr);

entry.key_ptr.* = std.math.cast(Index, table.string_bytes.items.len) orelse return error.OutOfMemory;
try table.string_bytes.ensureUnusedCapacity(allocator, key.len + 1);

table.string_bytes.appendSliceAssumeCapacity(key);
table.string_bytes.appendAssumeCapacity('\x00');
}
return entry.key_ptr.*;
}

/// Returns a null-terminated string given the index
/// complexity: O(1)
pub fn string(table: *StringTable, idx: Index) [:0]const u8 {
/// complexity: O(n)
pub fn string(table: *const StringTable, idx: Index) [:0]const u8 {
return std.mem.span(@as([*:0]const u8, @ptrCast(table.string_bytes.items.ptr)) + idx);
}

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