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|
use encoding::utf8;
use endian;
use fmt;
use io;
use strings;
use trace;
use uuid;
export type Decoder = struct {
input: []u8,
pos: size,
tracer: *trace::tracer,
};
export type Context = struct {
dec: *Decoder,
pos: size,
fmt: str,
fields: []fmt::field,
up: nullable *Context,
};
export fn log(
ctx: *Context,
lvl: trace::level,
fmt: str,
fields: fmt::field...
) void = {
log_(ctx, null, lvl, fmt, fields...);
};
fn log_(
ctx: *Context,
trace_ctx: nullable *trace::context,
lvl: trace::level,
fmt: str,
fields: fmt::field...
) void = {
let s = "";
defer free(s);
if (len(ctx.fmt) != 0) {
s = fmt::asprintf(ctx.fmt, ctx.fields...);
// TODO: is this legal? works at the moment due to qbe
// semantics, but who knows...
trace_ctx = &trace::context {
fmt = "{} (offset {})",
fields = [s, ctx.pos],
next = trace_ctx,
};
};
match (ctx.up) {
case let ctx_: *Context =>
log_(ctx_, trace_ctx, lvl, fmt, fields...);
case null =>
trace::log(ctx.dec.tracer, trace_ctx, lvl, fmt, fields...);
};
};
export fn error(ctx: *Context, fmt: str, fields: fmt::field...) trace::failed = {
log(ctx, trace::level::ERROR, fmt, fields...);
return trace::failed;
};
export fn root(dec: *Decoder) Context = {
return Context {
dec = dec,
pos = dec.pos,
...
};
};
export fn context(ctx: *Context, fmt: str, fields: fmt::field...) Context = {
return Context {
dec = ctx.dec,
pos = ctx.dec.pos,
fmt = fmt,
fields = fields,
up = ctx,
};
};
export fn decode_nbytes(ctx: *Context, length: size)
([]u8 | trace::failed) = {
const dec = ctx.dec;
if (len(dec.input) - dec.pos < length) {
return error(ctx, "Expected {} bytes, found only {}",
length, len(dec.input) - dec.pos);
};
const res = dec.input[dec.pos..dec.pos + length];
dec.pos += length;
return res;
};
export fn decode_byte(ctx: *Context) (u8 | trace::failed) = {
const b = decode_nbytes(ctx, 1)?;
return b[0];
};
export fn decode_short(ctx: *Context) (u16 | trace::failed) = {
const b = decode_nbytes(ctx, 2)?;
return endian::begetu16(b);
};
export fn decode_int(ctx: *Context) (u32 | trace::failed) = {
const b = decode_nbytes(ctx, 4)?;
return endian::begetu32(b);
};
export fn decode_long(ctx: *Context) (u64 | trace::failed) = {
const b = decode_nbytes(ctx, 8)?;
return endian::begetu64(b);
};
export fn decode_bool(ctx: *Context) (bool | trace::failed) = {
const b = decode_byte(ctx)?;
if (b >= 2) {
return error(ctx, "Invalid boolean");
};
return b != 0;
};
export fn decode_float(ctx: *Context) (f32 | trace::failed) = {
const v = decode_int(ctx)?;
return *(&v: *f32);
};
export fn decode_double(ctx: *Context) (f64 | trace::failed) = {
const v = decode_long(ctx)?;
return *(&v: *f64);
};
export fn try_decode_varint(ctx: *Context) (i32 | !(trace::failed | TooShort)) = {
let res = 0u32;
const dec = ctx.dec;
for (let i = 0u32; dec.pos + i < len(dec.input); i += 1) {
const b = dec.input[dec.pos + i];
if (i == 4 && b & 0xf0 != 0) {
return error(ctx, "VarInt too long");
};
res |= (b & 0x7f): u32 << (7 * i);
if (b & 0x80 == 0) {
dec.pos += i + 1;
return res: i32;
};
};
return TooShort;
};
export fn decode_varint(ctx: *Context) (i32 | trace::failed) = {
match (try_decode_varint(ctx)) {
case let res: i32 =>
return res;
case =>
return error(ctx, "VarInt too short");
};
};
export fn decode_string(ctx: *Context, maxlen: size) (str | trace::failed) = {
const length = decode_varint(&context(ctx, "string length"))?;
const length = length: size;
if (length >= maxlen * 4) {
return error(ctx,
"String length {} exceeds limit of {} bytes",
length, maxlen * 4);
};
const ctx_ = context(ctx, "string data ({} bytes)", length);
const bytes = decode_nbytes(&ctx_, length)?;
match (strings::fromutf8(bytes)) {
case let string: str =>
// don't bother checking length in code points. doesn't seem
// very useful.
return string;
case utf8::invalid =>
return error(&ctx_, "Invalid UTF-8");
};
};
export fn decode_uuid(ctx: *Context) (uuid::uuid | trace::failed) = {
let uuid: [16]u8 = [0...];
uuid[..] = decode_nbytes(ctx, 16)?;
return uuid;
};
export fn expect_end(ctx: *Context) (void | trace::failed) = {
if (ctx.dec.pos != len(ctx.dec.input)) {
return error(ctx,
"Expected end of input, but found {} extra bytes starting at {}",
len(ctx.dec.input) - ctx.dec.pos, ctx.dec.pos);
};
};
|
