marshal.gr

/**
 * Utilities for serializing and deserializing Grain data.
 *
 * @example from "marshal" include Marshal
 *
 * @since v0.5.3
 */
module Marshal

/*
  SERIALIZED BINARY FORMAT

  Grain stack-allocated values are serialized as-is. Heap-allocated values are
  largely serialized the same as their in-memory representation, with the
  exception that pointers are offsets into the byte sequence rather than
  pointers into memory. Structures are kept 8-byte aligned to be consistent
  with Grain's in-memory representation. The order in which these structures
  appear in the byte sequence is not significant.

  The first 32-bit value in the byte sequence is either a stack-allocated value
  or a "pointer" to a heap-allocated value.
*/

from "runtime/unsafe/wasmi32" include WasmI32
use WasmI32.{
  (+),
  (*),
  (&),
  (==),
  (!=),
  gtU as (>),
  ltU as (<),
  leU as (<=),
  load,
  store,
  fromGrain,
  toGrain,
}
from "runtime/unsafe/wasmi64" include WasmI64
from "runtime/unsafe/memory" include Memory
from "runtime/unsafe/tags" include Tags
from "runtime/dataStructures" include DataStructures
use DataStructures.{ allocateBytes, newInt32 }
from "map" include Map
from "set" include Set

@unsafe
let roundTo8 = n => {
  n + 7n & 0xfffffff8n
}

@unsafe
let isHeapPtr = value =>
  (value & Tags._GRAIN_GENERIC_TAG_MASK) == Tags._GRAIN_GENERIC_HEAP_TAG_TYPE

@unsafe
let rec size = (value, acc, valuesSeen, toplevel) => {
  if (isHeapPtr(value)) {
    let asInt32 = toGrain(newInt32(value)): Int32
    if (Set.contains(asInt32, valuesSeen)) {
      // We've detected a cycle, and we'll refer to the existing instance
      acc
    } else {
      Set.add(asInt32, valuesSeen)

      let acc = if (toplevel) {
        // We'll write a word (and 32 bits of padding) to indicate that this is a heap value
        acc + 8n
      } else {
        acc
      }
      let heapPtr = value
      match (load(heapPtr, 0n)) {
        t when t == Tags._GRAIN_STRING_HEAP_TAG ||
          t == Tags._GRAIN_BYTES_HEAP_TAG => {
          acc + roundTo8(8n + load(heapPtr, 4n))
        },
        t when t == Tags._GRAIN_ADT_HEAP_TAG => {
          let arity = load(heapPtr, 16n)

          let mut acc = acc + roundTo8(20n + arity * 4n)

          let a = arity * 4n
          for (let mut i = 0n; i < a; i += 4n) {
            acc = size(load(heapPtr + i, 20n), acc, valuesSeen, false)
          }

          acc
        },
        t when t == Tags._GRAIN_RECORD_HEAP_TAG => {
          let arity = load(heapPtr, 12n)

          let mut acc = acc + roundTo8(16n + arity * 4n)

          let a = arity * 4n
          for (let mut i = 0n; i < a; i += 4n) {
            acc = size(load(heapPtr + i, 16n), acc, valuesSeen, false)
          }

          acc
        },
        t when t == Tags._GRAIN_ARRAY_HEAP_TAG => {
          let arity = load(heapPtr, 4n)

          let mut acc = acc + roundTo8(8n + arity * 4n)

          let a = arity * 4n
          for (let mut i = 0n; i < a; i += 4n) {
            acc = size(load(heapPtr + i, 8n), acc, valuesSeen, false)
          }

          acc
        },
        t when t == Tags._GRAIN_TUPLE_HEAP_TAG => {
          let arity = load(heapPtr, 4n)

          let mut acc = acc + roundTo8(8n + arity * 4n)

          let l = arity * 4n
          for (let mut i = 0n; i < l; i += 4n) {
            acc = size(load(heapPtr + i, 8n), acc, valuesSeen, false)
          }

          acc
        },
        t when t == Tags._GRAIN_LAMBDA_HEAP_TAG => {
          let arity = load(heapPtr, 12n)

          let mut acc = acc + roundTo8(16n + arity * 4n)

          let a = arity * 4n
          for (let mut i = 0n; i < a; i += 4n) {
            acc = size(load(heapPtr + i, 16n), acc, valuesSeen, false)
          }

          acc
        },
        t when t == Tags._GRAIN_BOXED_NUM_HEAP_TAG => {
          let tag = load(heapPtr, 4n)
          match (tag) {
            t when t == Tags._GRAIN_INT64_BOXED_NUM_TAG ||
              t == Tags._GRAIN_FLOAT64_BOXED_NUM_TAG => {
              acc + 16n
            },
            t when t == Tags._GRAIN_BIGINT_BOXED_NUM_TAG => {
              acc + 16n + load(heapPtr, 8n) * 8n
            },
            t when t == Tags._GRAIN_RATIONAL_BOXED_NUM_TAG => {
              acc +
                16n +
                size(load(value, 8n), 0n, valuesSeen, false) +
                size(load(value, 12n), 0n, valuesSeen, false)
            },
            _ => {
              fail "Unknown number type"
            },
          }
        },
        t when t == Tags._GRAIN_INT32_HEAP_TAG ||
          t == Tags._GRAIN_FLOAT32_HEAP_TAG ||
          t == Tags._GRAIN_UINT32_HEAP_TAG => {
          acc + 8n
        },
        t when t == Tags._GRAIN_UINT64_HEAP_TAG => {
          // 16 for alignment
          acc + 16n
        },
        _ => {
          fail "Unknown heap type"
        },
      }
    }
  } else {
    // Handle non-heap values: booleans, chars, void, etc.
    if (toplevel) {
      acc + 4n
    } else {
      acc
    }
  }
}

@unsafe
let size = value => {
  size(value, 0n, Set.make(), true)
}

@unsafe
let rec marshalHeap = (heapPtr, buf, offset, valuesSeen) => {
  let asInt32 = toGrain(newInt32(heapPtr)): Int32
  let offsetAsInt32 = toGrain(newInt32(offset)): Int32
  Map.set(asInt32, offsetAsInt32, valuesSeen)

  match (load(heapPtr, 0n)) {
    t when t == Tags._GRAIN_STRING_HEAP_TAG || t == Tags._GRAIN_BYTES_HEAP_TAG => {
      let size = 8n + load(heapPtr, 4n)
      Memory.copy(buf + offset, heapPtr, size)
      roundTo8(offset + size)
    },
    t when t == Tags._GRAIN_ADT_HEAP_TAG => {
      Memory.copy(buf + offset, heapPtr, 20n)

      let arity = load(heapPtr, 16n)

      let mut payloadOffset = roundTo8(offset + 20n + arity * 4n)

      let a = arity * 4n
      for (let mut i = 0n; i < a; i += 4n) {
        let value = load(heapPtr + i, 20n)
        if (isHeapPtr(value)) {
          let asInt32 = toGrain(newInt32(value)): Int32
          match (Map.get(asInt32, valuesSeen)) {
            Some(value) => {
              let ptr = load(fromGrain(value), 4n)
              store(buf, ptr, offset + i + 20n)
            },
            None => {
              store(buf, payloadOffset, offset + i + 20n)
              payloadOffset = marshalHeap(value, buf, payloadOffset, valuesSeen)
            },
          }
        } else {
          store(buf, value, offset + i + 20n)
        }
      }

      payloadOffset
    },
    t when t == Tags._GRAIN_RECORD_HEAP_TAG => {
      Memory.copy(buf + offset, heapPtr, 16n)

      let arity = load(heapPtr, 12n)

      let mut payloadOffset = roundTo8(offset + 16n + arity * 4n)

      let a = arity * 4n
      for (let mut i = 0n; i < a; i += 4n) {
        let value = load(heapPtr + i, 16n)
        if (isHeapPtr(value)) {
          let asInt32 = toGrain(newInt32(value)): Int32
          match (Map.get(asInt32, valuesSeen)) {
            Some(value) => {
              let ptr = load(fromGrain(value), 4n)
              store(buf, ptr, offset + i + 16n)
            },
            None => {
              store(buf, payloadOffset, offset + i + 16n)
              payloadOffset = marshalHeap(value, buf, payloadOffset, valuesSeen)
            },
          }
        } else {
          store(buf, value, offset + i + 16n)
        }
      }

      payloadOffset
    },
    t when t == Tags._GRAIN_ARRAY_HEAP_TAG => {
      Memory.copy(buf + offset, heapPtr, 8n)

      let arity = load(heapPtr, 4n)

      let mut payloadOffset = roundTo8(offset + 8n + arity * 4n)

      let a = arity * 4n
      for (let mut i = 0n; i < a; i += 4n) {
        let value = load(heapPtr + i, 8n)
        if (isHeapPtr(value)) {
          let asInt32 = toGrain(newInt32(value)): Int32
          match (Map.get(asInt32, valuesSeen)) {
            Some(value) => {
              let ptr = load(fromGrain(value), 4n)
              store(buf, ptr, offset + i + 8n)
            },
            None => {
              store(buf, payloadOffset, offset + i + 8n)
              payloadOffset = marshalHeap(value, buf, payloadOffset, valuesSeen)
            },
          }
        } else {
          store(buf, value, offset + i + 8n)
        }
      }

      payloadOffset
    },
    t when t == Tags._GRAIN_TUPLE_HEAP_TAG => {
      Memory.copy(buf + offset, heapPtr, 8n)

      let arity = load(heapPtr, 4n)

      let mut payloadOffset = roundTo8(offset + 8n + arity * 4n)

      let a = arity * 4n
      for (let mut i = 0n; i < a; i += 4n) {
        let value = load(heapPtr + i, 8n)
        if (isHeapPtr(value)) {
          let asInt32 = toGrain(newInt32(value)): Int32
          match (Map.get(asInt32, valuesSeen)) {
            Some(value) => {
              let ptr = load(fromGrain(value), 4n)
              store(buf, ptr, offset + i + 8n)
            },
            None => {
              store(buf, payloadOffset, offset + i + 8n)
              payloadOffset = marshalHeap(value, buf, payloadOffset, valuesSeen)
            },
          }
        } else {
          store(buf, value, offset + i + 8n)
        }
      }

      payloadOffset
    },
    t when t == Tags._GRAIN_LAMBDA_HEAP_TAG => {
      Memory.copy(buf + offset, heapPtr, 16n)

      let arity = load(heapPtr, 12n)

      let mut payloadOffset = roundTo8(offset + 16n + arity * 4n)

      let a = arity * 4n
      for (let mut i = 0n; i < a; i += 4n) {
        let value = load(heapPtr + i, 16n)
        if (isHeapPtr(value)) {
          let asInt32 = toGrain(newInt32(value)): Int32
          match (Map.get(asInt32, valuesSeen)) {
            Some(value) => {
              let ptr = load(fromGrain(value), 4n)
              store(buf, ptr, offset + i + 16n)
            },
            None => {
              store(buf, payloadOffset, offset + i + 16n)
              payloadOffset = marshalHeap(value, buf, payloadOffset, valuesSeen)
            },
          }
        } else {
          store(buf, value, offset + i + 16n)
        }
      }

      payloadOffset
    },
    t when t == Tags._GRAIN_BOXED_NUM_HEAP_TAG => {
      let tag = load(heapPtr, 4n)
      match (tag) {
        t when t == Tags._GRAIN_INT64_BOXED_NUM_TAG => {
          Memory.copy(buf + offset, heapPtr, 16n)
          offset + 16n
        },
        t when t == Tags._GRAIN_BIGINT_BOXED_NUM_TAG => {
          let size = 16n + load(heapPtr, 8n) * 8n
          Memory.copy(buf + offset, heapPtr, size)
          offset + size
        },
        t when t == Tags._GRAIN_FLOAT64_BOXED_NUM_TAG => {
          Memory.copy(buf + offset, heapPtr, 16n)
          offset + 16n
        },
        t when t == Tags._GRAIN_RATIONAL_BOXED_NUM_TAG => {
          Memory.copy(buf + offset, heapPtr, 8n)
          let payloadOffset = offset + 16n
          store(buf, payloadOffset, offset + 8n)
          let payloadOffset = marshalHeap(
            load(heapPtr, 8n),
            buf,
            payloadOffset,
            valuesSeen
          )
          store(buf, payloadOffset, offset + 12n)
          let payloadOffset = marshalHeap(
            load(heapPtr, 12n),
            buf,
            payloadOffset,
            valuesSeen
          )
          payloadOffset
        },
        _ => {
          fail "Unknown number type"
        },
      }
    },
    t when t == Tags._GRAIN_INT32_HEAP_TAG ||
      t == Tags._GRAIN_FLOAT32_HEAP_TAG ||
      t == Tags._GRAIN_UINT32_HEAP_TAG => {
      Memory.copy(buf + offset, heapPtr, 8n)
      offset + 8n
    },
    t when t == Tags._GRAIN_UINT64_HEAP_TAG => {
      Memory.copy(buf + offset, heapPtr, 16n)
      offset + 16n
    },
    _ => {
      fail "Unknown heap type"
    },
  }
}

@unsafe
let marshal = (value, buf) => {
  if (isHeapPtr(value)) {
    store(buf, 8n, 0n)
    marshalHeap(value, buf, 8n, Map.make())
  } else {
    // Handle non-heap values: booleans, numbers, chars, void, etc.
    store(buf, value, 0n)
    4n
  }
}

/**
 * Serialize a value into a byte-based representation suitable for transmission
 * across a network or disk storage. The byte-based representation can be
 * deserialized at a later time to restore the value.
 *
 * @param value: The value to serialize
 * @returns A byte-based representation of the value
 *
 * @since v0.5.3
 */
@unsafe
provide let marshal = value => {
  let valuePtr = fromGrain(value)
  let size = size(valuePtr)
  let buf = allocateBytes(size)
  Memory.fill(buf + 8n, 0n, size)
  marshal(valuePtr, buf + 8n)
  ignore(value)
  toGrain(buf): Bytes
}

@unsafe
let reportError = (message, offset) => {
  Some(message ++ " at offset " ++ toString(toGrain(newInt32(offset))))
}

// When Grain has exception handling, validation could potentially occur during
// unmarshaling.

@unsafe
let validateStack = (value, offset) => {
  match (value) {
    _ when value == fromGrain(true) ||
      value == fromGrain(false) ||
      value == fromGrain(void) ||
      (value & Tags._GRAIN_NUMBER_TAG_MASK) == Tags._GRAIN_NUMBER_TAG_TYPE ||
      (value & Tags._GRAIN_GENERIC_TAG_MASK) == Tags._GRAIN_SHORTVAL_TAG_TYPE =>
      None,
    _ => reportError("Unknown value", offset),
  }
}

@unsafe
let rec validateHeap = (buf, bufSize, offset, valuesChecked) => {
  let offsetAsInt32 = toGrain(newInt32(offset)): Int32
  Set.add(offsetAsInt32, valuesChecked)

  let valuePtr = buf + offset
  match (load(valuePtr, 0n)) {
    t when t == Tags._GRAIN_STRING_HEAP_TAG || t == Tags._GRAIN_BYTES_HEAP_TAG => {
      let size = 8n + load(valuePtr, 4n)
      if (offset + size > bufSize) {
        return reportError("String/Bytes length exceeds buffer size", offset)
      }
    },
    t when t == Tags._GRAIN_ADT_HEAP_TAG => {
      let arity = load(valuePtr, 16n)
      let size = 20n + arity * 4n

      if (offset + size > bufSize) {
        return reportError("Enum payload size exceeds buffer size", offset)
      }

      let a = arity * 4n
      for (let mut i = 0n; i < a; i += 4n) {
        let value = load(valuePtr + i, 20n)
        if (isHeapPtr(value)) {
          let asInt32 = toGrain(newInt32(value)): Int32
          if (Set.contains(asInt32, valuesChecked)) {
            continue
          }
          match (validateHeap(buf, bufSize, value, valuesChecked)) {
            Some(e) => return Some(e),
            None => void,
          }
        } else {
          match (validateStack(value, offset)) {
            Some(e) => return Some(e),
            None => void,
          }
        }
      }
    },
    t when t == Tags._GRAIN_RECORD_HEAP_TAG => {
      let arity = load(valuePtr, 12n)
      let size = 16n + arity * 4n

      if (offset + size > bufSize) {
        return reportError("Record payload size exceeds buffer size", offset)
      }

      let a = arity * 4n
      for (let mut i = 0n; i < a; i += 4n) {
        let value = load(valuePtr + i, 16n)
        if (isHeapPtr(value)) {
          let asInt32 = toGrain(newInt32(value)): Int32
          if (Set.contains(asInt32, valuesChecked)) {
            continue
          }
          match (validateHeap(buf, bufSize, value, valuesChecked)) {
            Some(e) => return Some(e),
            None => void,
          }
        } else {
          match (validateStack(value, offset)) {
            Some(e) => return Some(e),
            None => void,
          }
        }
      }
    },
    t when t == Tags._GRAIN_ARRAY_HEAP_TAG => {
      let arity = load(valuePtr, 4n)
      let size = 8n + arity * 4n

      if (offset + size > bufSize) {
        return reportError("Array payload size exceeds buffer size", offset)
      }

      let a = arity * 4n
      for (let mut i = 0n; i < a; i += 4n) {
        let value = load(valuePtr + i, 8n)
        if (isHeapPtr(value)) {
          let asInt32 = toGrain(newInt32(value)): Int32
          if (Set.contains(asInt32, valuesChecked)) {
            continue
          }
          match (validateHeap(buf, bufSize, value, valuesChecked)) {
            Some(e) => return Some(e),
            None => void,
          }
        } else {
          match (validateStack(value, offset)) {
            Some(e) => return Some(e),
            None => void,
          }
        }
      }
    },
    t when t == Tags._GRAIN_TUPLE_HEAP_TAG => {
      let arity = load(valuePtr, 4n)
      let size = 8n + arity * 4n

      if (offset + size > bufSize) {
        return reportError("Tuple payload size exceeds buffer size", offset)
      }

      let a = arity * 4n
      for (let mut i = 0n; i < a; i += 4n) {
        let value = load(valuePtr + i, 8n)
        if (isHeapPtr(value)) {
          let asInt32 = toGrain(newInt32(value)): Int32
          if (Set.contains(asInt32, valuesChecked)) {
            continue
          }
          match (validateHeap(buf, bufSize, value, valuesChecked)) {
            Some(e) => return Some(e),
            None => void,
          }
        } else {
          match (validateStack(value, offset)) {
            Some(e) => return Some(e),
            None => void,
          }
        }
      }
    },
    t when t == Tags._GRAIN_LAMBDA_HEAP_TAG => {
      let arity = load(valuePtr, 12n)
      let size = 16n + arity * 4n

      if (offset + size > bufSize) {
        return reportError("Closure payload size exceeds buffer size", offset)
      }

      let a = arity * 4n
      for (let mut i = 0n; i < a; i += 4n) {
        let value = load(valuePtr + i, 16n)
        if (isHeapPtr(value)) {
          let asInt32 = toGrain(newInt32(value)): Int32
          if (Set.contains(asInt32, valuesChecked)) {
            continue
          }
          match (validateHeap(buf, bufSize, value, valuesChecked)) {
            Some(e) => return Some(e),
            None => void,
          }
        } else {
          match (validateStack(value, offset)) {
            Some(e) => return Some(e),
            None => void,
          }
        }
      }
    },
    t when t == Tags._GRAIN_BOXED_NUM_HEAP_TAG => {
      let tag = load(valuePtr, 4n)
      match (tag) {
        t when t == Tags._GRAIN_INT64_BOXED_NUM_TAG => {
          if (offset + 16n > bufSize) {
            return reportError(
              "Not enough bytes remaining in buffer for Int64/Number",
              offset
            )
          }
        },
        t when t == Tags._GRAIN_BIGINT_BOXED_NUM_TAG => {
          let size = 16n + load(valuePtr, 8n) * 8n
          if (offset + size > bufSize) {
            return reportError(
              "BigInt/Number payload size exeeds buffer size",
              offset
            )
          }
        },
        t when t == Tags._GRAIN_FLOAT64_BOXED_NUM_TAG => {
          if (offset + 16n > bufSize) {
            return reportError(
              "Not enough bytes remaining in buffer for Float64/Number",
              offset
            )
          }
        },
        t when t == Tags._GRAIN_RATIONAL_BOXED_NUM_TAG => {
          if (offset + 16n > bufSize) {
            return reportError(
              "Not enough bytes remaining in buffer for Rational/Number",
              offset
            )
          } else {
            let numeratorOffset = load(valuePtr, 8n)
            let denominatorOffset = load(valuePtr, 12n)
            match (validateHeap(buf, bufSize, numeratorOffset, valuesChecked)) {
              Some(err) => return Some(err),
              None => void,
            }
            match (validateHeap(buf, bufSize, denominatorOffset, valuesChecked)) {
              Some(err) => return Some(err),
              None => void,
            }
            if (
              load(buf, numeratorOffset) != Tags._GRAIN_BOXED_NUM_HEAP_TAG &&
              load(buf, numeratorOffset + 4n) !=
                Tags._GRAIN_BIGINT_BOXED_NUM_TAG
            ) {
              return reportError(
                "Rational/Number numerator was not in the expected format",
                offset
              )
            }
            if (
              load(buf, denominatorOffset) != Tags._GRAIN_BOXED_NUM_HEAP_TAG &&
              load(buf, denominatorOffset + 4n) !=
                Tags._GRAIN_BIGINT_BOXED_NUM_TAG
            ) {
              return reportError(
                "Rational/Number denominator was not in the expected format",
                offset
              )
            }
            match (validateHeap(buf, bufSize, denominatorOffset, valuesChecked)) {
              Some(e) => return Some(e),
              None => void,
            }
            if (
              load(buf, numeratorOffset) != Tags._GRAIN_BOXED_NUM_HEAP_TAG &&
              load(buf, numeratorOffset + 4n) !=
                Tags._GRAIN_BIGINT_BOXED_NUM_TAG
            ) {
              return reportError(
                "Rational/Number numerator was not in the expected format",
                offset
              )
            }
            let denominatorError = if (
              load(buf, denominatorOffset) != Tags._GRAIN_BOXED_NUM_HEAP_TAG &&
              load(buf, denominatorOffset + 4n) !=
                Tags._GRAIN_BIGINT_BOXED_NUM_TAG
            ) {
              return reportError(
                "Rational/Number denominator was not in the expected format",
                offset
              )
            }
          }
        },
        _ => void,
      }
    },
    t when t == Tags._GRAIN_INT32_HEAP_TAG => {
      if (offset + 8n > bufSize) {
        return reportError(
          "Not enough bytes remaining in buffer for Int32",
          offset
        )
      }
    },
    t when t == Tags._GRAIN_FLOAT32_HEAP_TAG => {
      if (offset + 8n > bufSize) {
        return reportError(
          "Not enough bytes remaining in buffer for Float32",
          offset
        )
      }
    },
    t when t == Tags._GRAIN_UINT32_HEAP_TAG => {
      if (offset + 8n > bufSize) {
        return reportError(
          "Not enough bytes remaining in buffer for Uint32",
          offset
        )
      }
    },
    t when t == Tags._GRAIN_UINT64_HEAP_TAG => {
      if (offset + 16n > bufSize) {
        return reportError(
          "Not enough bytes remaining in buffer for Uint64",
          offset
        )
      }
    },
    _ => void,
  }
  return None
}

@unsafe
let validate = (buf, bufSize) => {
  if (bufSize < 4n) {
    reportError("No bytes remaining in buffer", 0n)
  } else {
    let value = load(buf, 0n)
    if (isHeapPtr(value)) {
      validateHeap(buf, bufSize, value, Set.make())
    } else {
      // Handle non-heap values: booleans, chars, void, etc.
      match (value) {
        _ when value == fromGrain(true) ||
          value == fromGrain(false) ||
          value == fromGrain(void) ||
          (value & Tags._GRAIN_NUMBER_TAG_MASK) == Tags._GRAIN_NUMBER_TAG_TYPE ||
          (value & Tags._GRAIN_GENERIC_TAG_MASK) ==
            Tags._GRAIN_SHORTVAL_TAG_TYPE => None,
        _ => reportError("Unknown value", 0n),
      }
    }
  }
}

@unsafe
let rec unmarshalHeap = (buf, offset, valuesUnmarshaled) => {
  let offsetAsInt32 = toGrain(newInt32(offset)): Int32

  let valuePtr = buf + offset
  match (load(valuePtr, 0n)) {
    t when t == Tags._GRAIN_STRING_HEAP_TAG || t == Tags._GRAIN_BYTES_HEAP_TAG => {
      let size = 8n + load(valuePtr, 4n)
      let value = Memory.malloc(size)
      Memory.copy(value, valuePtr, size)

      let asInt32 = toGrain(newInt32(value)): Int32
      Map.set(offsetAsInt32, asInt32, valuesUnmarshaled)

      value
    },
    t when t == Tags._GRAIN_ADT_HEAP_TAG => {
      let arity = load(valuePtr, 16n)
      let size = 20n + arity * 4n

      let value = Memory.malloc(size)
      Memory.copy(value, valuePtr, 20n)

      let asInt32 = toGrain(newInt32(value)): Int32
      Map.set(offsetAsInt32, asInt32, valuesUnmarshaled)

      let a = arity * 4n
      for (let mut i = 0n; i < a; i += 4n) {
        let subvalue = load(valuePtr + i, 20n)
        if (isHeapPtr(subvalue)) {
          let asInt32 = toGrain(newInt32(subvalue)): Int32
          match (Map.get(asInt32, valuesUnmarshaled)) {
            Some(ptr) => {
              let ptr = load(fromGrain(ptr), 4n)
              store(value + i, Memory.incRef(ptr), 20n)
            },
            None => {
              store(
                value + i,
                unmarshalHeap(buf, subvalue, valuesUnmarshaled),
                20n
              )
            },
          }
        } else {
          store(value + i, subvalue, 20n)
        }
      }

      value
    },
    t when t == Tags._GRAIN_RECORD_HEAP_TAG => {
      let arity = load(valuePtr, 12n)
      let size = 16n + arity * 4n

      let value = Memory.malloc(size)
      Memory.copy(value, valuePtr, 16n)

      let asInt32 = toGrain(newInt32(value)): Int32
      Map.set(offsetAsInt32, asInt32, valuesUnmarshaled)

      let a = arity * 4n
      for (let mut i = 0n; i < a; i += 4n) {
        let subvalue = load(valuePtr + i, 16n)
        if (isHeapPtr(subvalue)) {
          let asInt32 = toGrain(newInt32(subvalue)): Int32
          match (Map.get(asInt32, valuesUnmarshaled)) {
            Some(ptr) => {
              let ptr = load(fromGrain(ptr), 4n)
              store(value + i, Memory.incRef(ptr), 16n)
            },
            None => {
              store(
                value + i,
                unmarshalHeap(buf, subvalue, valuesUnmarshaled),
                16n
              )
            },
          }
        } else {
          store(value + i, subvalue, 16n)
        }
      }

      value
    },
    t when t == Tags._GRAIN_ARRAY_HEAP_TAG => {
      let arity = load(valuePtr, 4n)
      let size = 8n + arity * 4n

      let value = Memory.malloc(size)
      Memory.copy(value, valuePtr, 8n)

      let asInt32 = toGrain(newInt32(value)): Int32
      Map.set(offsetAsInt32, asInt32, valuesUnmarshaled)

      let a = arity * 4n
      for (let mut i = 0n; i < a; i += 4n) {
        let subvalue = load(valuePtr + i, 8n)
        if (isHeapPtr(subvalue)) {
          let asInt32 = toGrain(newInt32(subvalue)): Int32
          match (Map.get(asInt32, valuesUnmarshaled)) {
            Some(ptr) => {
              let ptr = load(fromGrain(ptr), 4n)
              store(value + i, Memory.incRef(ptr), 8n)
            },
            None => {
              store(
                value + i,
                unmarshalHeap(buf, subvalue, valuesUnmarshaled),
                8n
              )
            },
          }
        } else {
          store(value + i, subvalue, 8n)
        }
      }

      value
    },
    t when t == Tags._GRAIN_TUPLE_HEAP_TAG => {
      let arity = load(valuePtr, 4n)
      let size = 8n + arity * 4n

      let value = Memory.malloc(size)
      Memory.copy(value, valuePtr, 8n)

      let asInt32 = toGrain(newInt32(value)): Int32
      Map.set(offsetAsInt32, asInt32, valuesUnmarshaled)

      let a = arity * 4n
      for (let mut i = 0n; i < a; i += 4n) {
        let subvalue = load(valuePtr + i, 8n)
        if (isHeapPtr(subvalue)) {
          let asInt32 = toGrain(newInt32(subvalue)): Int32
          match (Map.get(asInt32, valuesUnmarshaled)) {
            Some(ptr) => {
              let ptr = load(fromGrain(ptr), 4n)
              store(value + i, Memory.incRef(ptr), 8n)
            },
            None => {
              store(
                value + i,
                unmarshalHeap(buf, subvalue, valuesUnmarshaled),
                8n
              )
            },
          }
        } else {
          store(value + i, subvalue, 8n)
        }
      }

      value
    },
    t when t == Tags._GRAIN_LAMBDA_HEAP_TAG => {
      let arity = load(valuePtr, 12n)
      let size = 16n + arity * 4n

      let value = Memory.malloc(size)
      Memory.copy(value, valuePtr, 16n)

      let asInt32 = toGrain(newInt32(value)): Int32
      Map.set(offsetAsInt32, asInt32, valuesUnmarshaled)

      let a = arity * 4n
      for (let mut i = 0n; i < a; i += 4n) {
        let subvalue = load(valuePtr + i, 16n)
        if (isHeapPtr(subvalue)) {
          let asInt32 = toGrain(newInt32(subvalue)): Int32
          match (Map.get(asInt32, valuesUnmarshaled)) {
            Some(ptr) => {
              let ptr = load(fromGrain(ptr), 4n)
              store(value + i, Memory.incRef(ptr), 16n)
            },
            None => {
              store(
                value + i,
                unmarshalHeap(buf, subvalue, valuesUnmarshaled),
                16n
              )
            },
          }
        } else {
          store(value + i, subvalue, 16n)
        }
      }

      value
    },
    t when t == Tags._GRAIN_BOXED_NUM_HEAP_TAG => {
      let tag = load(valuePtr, 4n)
      match (tag) {
        t when t == Tags._GRAIN_INT64_BOXED_NUM_TAG => {
          let value = Memory.malloc(16n)
          Memory.copy(value, valuePtr, 16n)

          let asInt32 = toGrain(newInt32(value)): Int32
          Map.set(offsetAsInt32, asInt32, valuesUnmarshaled)

          value
        },
        t when t == Tags._GRAIN_BIGINT_BOXED_NUM_TAG => {
          let size = 16n + load(valuePtr, 8n) * 8n
          let value = Memory.malloc(size)
          Memory.copy(value, valuePtr, size)

          let asInt32 = toGrain(newInt32(value)): Int32
          Map.set(offsetAsInt32, asInt32, valuesUnmarshaled)

          value
        },
        t when t == Tags._GRAIN_FLOAT64_BOXED_NUM_TAG => {
          let value = Memory.malloc(16n)
          Memory.copy(value, valuePtr, 16n)

          let asInt32 = toGrain(newInt32(value)): Int32
          Map.set(offsetAsInt32, asInt32, valuesUnmarshaled)

          value
        },
        t when t == Tags._GRAIN_RATIONAL_BOXED_NUM_TAG => {
          let value = Memory.malloc(16n)
          Memory.copy(value, valuePtr, 8n)

          let asInt32 = toGrain(newInt32(value)): Int32
          Map.set(offsetAsInt32, asInt32, valuesUnmarshaled)

          let num = unmarshalHeap(buf, load(valuePtr, 8n), valuesUnmarshaled)
          store(value, num, 8n)
          let denom = unmarshalHeap(buf, load(valuePtr, 12n), valuesUnmarshaled)
          store(value, denom, 12n)
          value
        },
        _ => {
          fail "Unknown number type"
        },
      }
    },
    t when t == Tags._GRAIN_INT32_HEAP_TAG ||
      t == Tags._GRAIN_FLOAT32_HEAP_TAG ||
      t == Tags._GRAIN_UINT32_HEAP_TAG => {
      let value = Memory.malloc(8n)
      Memory.copy(value, valuePtr, 8n)

      let asInt32 = toGrain(newInt32(value)): Int32
      Map.set(offsetAsInt32, asInt32, valuesUnmarshaled)

      value
    },
    t when t == Tags._GRAIN_UINT64_HEAP_TAG => {
      let value = Memory.malloc(16n)
      Memory.copy(value, valuePtr, 16n)

      let asInt32 = toGrain(newInt32(value)): Int32
      Map.set(offsetAsInt32, asInt32, valuesUnmarshaled)

      value
    },
    _ => {
      fail "Unknown heap type"
    },
  }
}

@unsafe
let unmarshal = buf => {
  let value = load(buf, 0n)
  if (isHeapPtr(value)) {
    unmarshalHeap(buf, value, Map.make())
  } else {
    // Non-heap values: booleans, numbers, chars, void, etc.
    value
  }
}

/**
 * Deserialize the byte-based representation of a value back into an in-memory
 * value. This operation is not type-safe, and it is recommended that a type
 * annotation is used to declare the type of the unmarshaled value. While
 * attempts to unmarshal bad data will fail, this operation is still generally
 * unsafe and great care should be taken to ensure that the data being
 * unmarshaled corresponds to the expected type.
 *
 * @param bytes: The data to deserialize
 * @returns An in-memory value
 *
 * @since v0.5.3
 */
@unsafe
provide let unmarshal = (bytes: Bytes) => {
  let buf = fromGrain(bytes) + 8n
  let bufSize = load(fromGrain(bytes), 4n)
  match (validate(buf, bufSize)) {
    Some(error) => Err(error),
    None => Ok(toGrain(unmarshal(buf))),
  }
}