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package binary
import (
"bytes"
"fmt"
"github.com/tetratelabs/wazero/internal/leb128"
)
// decodeLimitsType returns the `limitsType` (min, max) decoded with the WebAssembly 1.0 (20191205) Binary Format.
//
// See https://www.w3.org/TR/2019/REC-wasm-core-1-20191205/#limits%E2%91%A6
//
// Extended in threads proposal: https://webassembly.github.io/threads/core/binary/types.html#limits
func decodeLimitsType(r *bytes.Reader) (min uint32, max *uint32, shared bool, err error) {
var flag byte
if flag, err = r.ReadByte(); err != nil {
err = fmt.Errorf("read leading byte: %v", err)
return
}
switch flag {
case 0x00, 0x02:
min, _, err = leb128.DecodeUint32(r)
if err != nil {
err = fmt.Errorf("read min of limit: %v", err)
}
case 0x01, 0x03:
min, _, err = leb128.DecodeUint32(r)
if err != nil {
err = fmt.Errorf("read min of limit: %v", err)
return
}
var m uint32
if m, _, err = leb128.DecodeUint32(r); err != nil {
err = fmt.Errorf("read max of limit: %v", err)
} else {
max = &m
}
default:
err = fmt.Errorf("%v for limits: %#x not in (0x00, 0x01, 0x02, 0x03)", ErrInvalidByte, flag)
}
shared = flag == 0x02 || flag == 0x03
return
}
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