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Update decode not to require type param
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@dadepo
dadepo committed Nov 16, 2024
1 parent 802178a commit 0b349de
Showing 1 changed file with 34 additions and 40 deletions.
74 changes: 34 additions & 40 deletions src/lib.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -124,25 +124,23 @@ pub fn encodeHexStr(comptime rawHexString: []const u8) ![encodedHexLen(rawHexStr
return out;
}

pub fn DecodeResult(comptime T: type) type {
return struct { decoded: T, rest: []const u8 };
}

pub const DecodeError = error{ NotMinimal, Overflow, Insufficient };
pub fn decode(comptime T: type, buf: []const u8) DecodeError!DecodeResult(T) {
var n: T = 0;
pub const DecodeResult = struct {
code: usize,
rest: []const u8,
};

pub const DecodeError = error{ NotMinimal, Insufficient };
pub fn decode(buf: []const u8) DecodeError!DecodeResult {
var n: usize = 0;
for (buf, 0..) |b, i| {
const k: u8 = @intCast(b & 0x7F);
n |= std.math.shl(T, k, (i * 7));
n |= std.math.shl(usize, k, (i * 7));
if ((b & 0x80) == 0) {
// last bit
if (b == 0 and i > 0) {
return error.NotMinimal;
}
return .{ .decoded = n, .rest = buf[i + 1 ..] };
}
if (i == (encodedTypelen(T) - 1)) {
return error.Overflow;
return .{ .code = n, .rest = buf[i + 1 ..] };
}
}
return error.Insufficient;
Expand Down Expand Up @@ -223,99 +221,95 @@ test "encodeHexStr==encodeHexStrAlloc" {
test "decode" {
{
const buf = ([1]u8{1});
const decoded = (try decode(u8, buf[0..]));
try std.testing.expectEqual(decoded.decoded, 1);
const decoded = (try decode(buf[0..]));
try std.testing.expectEqual(decoded.code, 1);
try std.testing.expectEqual(decoded.rest.len, 0);
}
{
const buf = ([1]u8{0b0111_1111});
const decoded = (try decode(u8, buf[0..]));
try std.testing.expectEqual(decoded.decoded, 127);
const decoded = (try decode(buf[0..]));
try std.testing.expectEqual(decoded.code, 127);
try std.testing.expectEqual(decoded.rest.len, 0);
}
{
const buf = ([2]u8{ 0b1000_0000, 1 });
const decoded = (try decode(u8, buf[0..]));
try std.testing.expectEqual(decoded.decoded, 128);
const decoded = (try decode(buf[0..]));
try std.testing.expectEqual(decoded.code, 128);
try std.testing.expectEqual(decoded.rest.len, 0);
}
{
// encode with remaining data.
const buf = ([3]u8{ 0b1000_0000, 1, 0b1000_0000 });
const decoded = (try decode(u8, buf[0..]));
try std.testing.expectEqual(decoded.decoded, 128);
const decoded = (try decode(buf[0..]));
try std.testing.expectEqual(decoded.code, 128);
try std.testing.expectEqual(decoded.rest[0], 0b1000_0000);
}
{
const buf = ([2]u8{ 0b1000_0000, 1 });
const decoded = (try decode(u8, buf[0..]));
try std.testing.expectEqual(decoded.decoded, 128);
const decoded = (try decode(buf[0..]));
try std.testing.expectEqual(decoded.code, 128);
try std.testing.expectEqual(decoded.rest.len, 0);
}
{
const buf = ([2]u8{ 0b1111_1111, 1 });
const decoded = (try decode(u8, buf[0..]));
try std.testing.expectEqual(decoded.decoded, 255);
const decoded = (try decode(buf[0..]));
try std.testing.expectEqual(decoded.code, 255);
try std.testing.expectEqual(decoded.rest.len, 0);
}
{
const buf = ([3]u8{ 0x80, 0x80, 1 });
const decoded = (try decode(u16, buf[0..]));
try std.testing.expectEqual(decoded.decoded, 16384);
const decoded = (try decode(buf[0..]));
try std.testing.expectEqual(decoded.code, 16384);
try std.testing.expectEqual(decoded.rest.len, 0);
}
{
const buf = ([2]u8{ 0b1010_1100, 0b0000_0010 });
const decoded = (try decode(u16, buf[0..]));
try std.testing.expectEqual(decoded.decoded, 300);
const decoded = (try decode(buf[0..]));
try std.testing.expectEqual(decoded.code, 300);
try std.testing.expectEqual(decoded.rest.len, 0);
}
{
const buf = ([10]u8{ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 1 });
const decoded = (try decode(u64, buf[0..]));
try std.testing.expectEqual(decoded.decoded, 0xFFFFFFFFFFFFFFFF);
const decoded = (try decode(buf[0..]));
try std.testing.expectEqual(decoded.code, 0xFFFFFFFFFFFFFFFF);
try std.testing.expectEqual(decoded.rest.len, 0);
}
// errors.
{
const buf = ([10]u8{ 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80 });
try std.testing.expectError(DecodeError.Overflow, decode(u64, buf[0..]));
}
{
const buf = ([9]u8{ 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80 });
try std.testing.expectError(DecodeError.Insufficient, decode(u64, buf[0..]));
try std.testing.expectError(DecodeError.Insufficient, decode(buf[0..]));
}
}

test "identity" {
{
for (0..std.math.maxInt(u8)) |n_| {
const n: u8 = @intCast(n_);
try std.testing.expectEqual(n, (try decode(u8, &encodeForType(u8, n))).decoded);
try std.testing.expectEqual(n, (try decode(&encodeForType(u8, n))).code);
}
}
{
for (0..std.math.maxInt(u16)) |n_| {
const n: u16 = @intCast(n_);
try std.testing.expectEqual(n, (try decode(u16, &encodeForType(u16, n))).decoded);
try std.testing.expectEqual(n, (try decode(&encodeForType(u16, n))).code);
}
}
{
for (0..1000_000) |n_| {
const n: u32 = @intCast(n_);
try std.testing.expectEqual(n, (try decode(u32, &encodeForType(u32, n))).decoded);
try std.testing.expectEqual(n, (try decode(&encodeForType(u32, n))).code);
}
}
{
for (0..1000_000) |n_| {
const n: u64 = @intCast(n_);
try std.testing.expectEqual(n, (try decode(u64, &encodeForType(u64, n))).decoded);
try std.testing.expectEqual(n, (try decode(&encodeForType(u64, n))).code);
}
}
{
for (0..1000_000) |n_| {
const n: u128 = @intCast(n_);
try std.testing.expectEqual(n, (try decode(u128, &encodeForType(u128, n))).decoded);
try std.testing.expectEqual(n, (try decode(&encodeForType(u128, n))).code);
}
}
}

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