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std.fmt.format: support {B} for human readable bytes

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This commit is contained in:
Andrew Kelley 2018-05-15 22:11:03 -04:00
parent 3625df25d6
commit 492a214d4c
1 changed files with 55 additions and 0 deletions
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55
std/fmt/index.zig
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@ -27,6 +27,8 @@ pub fn format(context: var, comptime Errors: type, output: fn(@typeOf(context),
Character,
Buf,
BufWidth,
Bytes,
BytesWidth,
};
comptime var start_index = 0;
@ -95,6 +97,10 @@ pub fn format(context: var, comptime Errors: type, output: fn(@typeOf(context),
'.' => {
state = State.Float;
},
'B' => {
width = 0;
state = State.Bytes;
},
else => @compileError("Unknown format character: " ++ []u8{c}),
},
State.Buf => switch (c) {
@ -206,6 +212,30 @@ pub fn format(context: var, comptime Errors: type, output: fn(@typeOf(context),
},
else => @compileError("Unexpected character in format string: " ++ []u8{c}),
},
State.Bytes => switch (c) {
'}' => {
try formatBytes(args[next_arg], 0, context, Errors, output);
next_arg += 1;
state = State.Start;
start_index = i + 1;
},
'0' ... '9' => {
width_start = i;
state = State.BytesWidth;
},
else => @compileError("Unexpected character in format string: " ++ []u8{c}),
},
State.BytesWidth => switch (c) {
'}' => {
width = comptime (parseUnsigned(usize, fmt[width_start..i], 10) catch unreachable);
try formatBytes(args[next_arg], width, context, Errors, output);
next_arg += 1;
state = State.Start;
start_index = i + 1;
},
'0' ... '9' => {},
else => @compileError("Unexpected character in format string: " ++ []u8{c}),
},
}
}
comptime {
@ -520,6 +550,25 @@ pub fn formatFloatDecimal(value: var, maybe_precision: ?usize, context: var, com
}
}
pub fn formatBytes(value: var, width: ?usize,
context: var, comptime Errors: type, output: fn(@typeOf(context), []const u8)Errors!void) Errors!void
{
if (value == 0) {
return output(context, "0B");
}
const mags = " KMGTPEZY";
const magnitude = math.min(math.log2(value) / 10, mags.len - 1);
const new_value = f64(value) / math.pow(f64, 1024, f64(magnitude));
const suffix = mags[magnitude];
try formatFloatDecimal(new_value, width, context, Errors, output);
if (suffix != ' ') {
try output(context, (&suffix)[0..1]);
}
return output(context, "B");
}
pub fn formatInt(value: var, base: u8, uppercase: bool, width: usize,
context: var, comptime Errors: type, output: fn(@typeOf(context), []const u8)Errors!void) Errors!void
@ -767,6 +816,12 @@ test "fmt.format" {
const result = try bufPrint(buf1[0..], "u3: {}\n", value);
assert(mem.eql(u8, result, "u3: 5\n"));
}
{
var buf1: [32]u8 = undefined;
const value: usize = 63 * 1024 * 1024;
const result = try bufPrint(buf1[0..], "file size: {B}\n", value);
assert(mem.eql(u8, result, "file size: 63MB\n"));
}
{
// Dummy field because of https://github.com/zig-lang/zig/issues/557.
const Struct = struct {