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Handle potential downcast when translating stream size

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This commit is contained in:
Benjamin Feng 2020-03-06 12:03:15 -06:00
parent 0059d9ee3e
commit 6a53fe7c93
2 changed files with 10 additions and 4 deletions
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4
lib/std/buffer.zig
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@ -65,7 +65,9 @@ pub const Buffer = struct {
}
pub fn allocPrint(allocator: *Allocator, comptime format: []const u8, args: var) !Buffer {
const size = std.fmtstream.count(format, args);
const size = std.fmtstream.count(format, args) catch |err| switch (err) {
error.Overflow => return error.OutOfMemory,
};
var self = try Buffer.initSize(allocator, size);
assert((std.fmtstream.bufPrint(self.list.items, format, args) catch unreachable).len == size);
return self;

10
lib/std/fmtstream.zig
View File

@ -1081,16 +1081,20 @@ pub fn bufPrint(buf: []u8, comptime fmt: []const u8, args: var) BufPrintError![]
}
// Count the characters needed for format. Useful for preallocating memory
pub fn count(comptime fmt: []const u8, args: var) usize {
pub fn count(comptime fmt: []const u8, args: var) !usize {
var counting_stream = std.io.countingOutStream(std.io.null_out_stream);
format(counting_stream.outStream(), fmt, args) catch |err| switch (err) {};
return counting_stream.bytes_written;
return std.math.cast(usize, counting_stream.bytes_written);
}
pub const AllocPrintError = error{OutOfMemory};
pub fn allocPrint(allocator: *mem.Allocator, comptime fmt: []const u8, args: var) AllocPrintError![]u8 {
const buf = try allocator.alloc(u8, count(fmt, args));
const size = count(fmt, args) catch |err| switch (err) {
// Output too long. Can't possibly allocate enough memory to display it.
error.Overflow => return error.OutOfMemory,
};
const buf = try allocator.alloc(u8, size);
return bufPrint(buf, fmt, args) catch |err| switch (err) {
error.BufferTooSmall => unreachable, // we just counted the size above
};