Refactor decodeField and get*

protobuf_serialization.nim

@@ -41,6 +41,8 @@ type
 
   AnyProtoType* = SomeVarint | SomeLengthDelimited | SomeFixed | object
 
+  UnexpectedTypeError* = object of ValueError
+
 proc newProtoBuffer*(): ProtoBuffer =
   ProtoBuffer(outstream: OutputStream.init(), fieldNum: 1)
 
@@ -111,12 +113,12 @@ proc encodeField(stream: OutputStreamVar, fieldNum: int, value: SomeFixed32) {.i
   stream.put(value)
 
 proc put(stream: OutputStreamVar, value: SomeLengthDelimited) {.inline.} =
+  stream.put(len(value).uint)
   for b in value:
     stream.append byte(b)
 
 proc encodeField(stream: OutputStreamVar, fieldNum: int, value: SomeLengthDelimited) {.inline.} =
   stream.append protoHeader(fieldNum, LengthDelimited)
-  stream.put(len(value).uint)
   stream.put(value)
 
 proc put(stream: OutputStreamVar, value: object) {.inline.}
@@ -131,7 +133,6 @@ proc encodeField(stream: OutputStreamVar, fieldNum: int, value: object) {.inline
   let objOutput = objStream.getOutput()
   if objOutput.len > 0:
     stream.append protoHeader(fieldNum, LengthDelimited)
-    stream.put(len(objOutput).uint)
     stream.put(objOutput)
 
 proc put(stream: OutputStreamVar, value: object) {.inline.} =
@@ -145,14 +146,14 @@ proc put(stream: OutputStreamVar, value: object) {.inline.} =
 proc encode*(protobuf: var ProtoBuffer, value: object) {.inline.} =
   protobuf.outstream.put(value)
 
-proc encodeField*(protobuf: var ProtoBuffer, value: AnyProtoType) {.inline.} =
-  protobuf.outstream.encodeField(protobuf.fieldNum, value)
-  inc protobuf.fieldNum
-
 proc encodeField*(protobuf: var ProtoBuffer, fieldNum: int, value: AnyProtoType) {.inline.} =
   protobuf.outstream.encodeField(fieldNum, value)
 
-proc getFixed*[T: SomeFixed](
+proc encodeField*(protobuf: var ProtoBuffer, value: AnyProtoType) {.inline.} =
+  protobuf.encodeField(protobuf.fieldNum, value)
+  inc protobuf.fieldNum
+
+proc get*[T: SomeFixed](
   bytes: var seq[byte],
   ty: typedesc[T],
   outOffset: var int,
@@ -173,7 +174,7 @@ proc getFixed*[T: SomeFixed](
 
   result = cast[T](value)
 
-proc getVarint[T: SomeVarint](
+proc get[T: SomeVarint](
   bytes: var seq[byte],
   ty: typedesc[T],
   outOffset: var int,
@@ -188,6 +189,7 @@ proc getVarint[T: SomeVarint](
     var value: byte
   else:
     var value: T
+
   var shiftAmount = 0
   while true:
     value += type(value)(bytes[outOffset] and 0b0111_1111) shl shiftAmount
@@ -206,53 +208,30 @@ proc getVarint[T: SomeVarint](
   else:
     result = T(value)
 
-proc decodeField*[T: SomeVarint](
+proc checkType[T: SomeVarint](tyByte: byte, ty: typedesc[T], offset: int) {.inline.} =
-  bytes: var seq[byte],
+  let wireTy = wireType(tyByte)
-  ty: typedesc[T],
-  outOffset: var int,
-  outBytesProcessed: var int,
-  numBytesToRead = none(int)
-): ProtoField[T] {.inline.} =
-  # Only up to 128 bits supported by the spec
-  assert sizeof(T) <= 16
-
-  var bytesRead = 0
-
-  let wireTy = wireType(bytes[outOffset])
   if wireTy != Varint:
-    raise newException(Exception, fmt"Not a varint at offset {outOffset}! Received a {wireTy}")
+    raise newException(UnexpectedTypeError, fmt"Not a varint at offset {offset}! Received a {wireTy}")
 
-  result.index = fieldNumber(bytes[outOffset])
+proc checkType[T: SomeFixed](tyByte: byte, ty: typedesc[T], offset: int) {.inline.} =
-  increaseBytesRead()
+  let wireTy = wireType(tyByte)
+  if wireTy notin {Fixed32, Fixed64}:
+    raise newException(UnexpectedTypeError, fmt"Not a fixed32 or fixed64 at offset {offset}! Received a {wireTy}")
 
-  result.value = getVarint(bytes, ty, outOffset, outBytesProcessed, numBytesToRead)
+proc checkType[T: SomeLengthDelimited](tyByte: byte, ty: typedesc[T], offset: int) {.inline.} =
+  let wireTy = wireType(tyByte)
+  if wireTy != LengthDelimited:
+    raise newException(UnexpectedTypeError, fmt"Not a length delimited value at offset {offset}! Received a {wireTy}")
 
-proc decodeField*[T: SomeFixed](
+proc get*[T: SomeLengthDelimited](
   bytes: var seq[byte],
   ty: typedesc[T],
   outOffset: var int,
   outBytesProcessed: var int,
   numBytesToRead = none(int)
-): ProtoField[T] {.inline.} =
-  var bytesRead = 0
-
-  let wireTy = wireType(bytes[outOffset])
-  if wireTy notin {Fixed32, Fixed64}:
-    raise newException(Exception, fmt"Not a fixed32 or fixed64 at offset {outOffset}! Received a {wireTy}")
-
-  result.index = fieldNumber(bytes[outOffset])
-  increaseBytesRead()
-
-  result.value = getFixed(bytes, ty, outOffset, outBytesProcessed, numBytesToRead)
-
-proc getLengthDelimited*[T: SomeLengthDelimited](
-  bytes: var seq[byte],
-  ty: typedesc[T], outOffset: var int,
-  outBytesProcessed: var int,
-  numBytesToRead = none(int)
 ): T {.inline.} =
   var bytesRead = 0
-  let decodedSize = getVarint(bytes, uint, outOffset, outBytesProcessed, numBytesToRead)
+  let decodedSize = bytes.get(uint, outOffset, outBytesProcessed, numBytesToRead)
   let length = decodedSize.int
 
   when T is string:
@@ -268,7 +247,7 @@ proc getLengthDelimited*[T: SomeLengthDelimited](
 
   increaseBytesRead(length)
 
-proc decodeField*[T: SomeLengthDelimited](
+proc decodeField*[T: SomeFixed | SomeVarint | SomeLengthDelimited](
   bytes: var seq[byte],
   ty: typedesc[T],
   outOffset: var int,
@@ -276,47 +255,21 @@ proc decodeField*[T: SomeLengthDelimited](
   numBytesToRead = none(int)
 ): ProtoField[T] {.inline.} =
   var bytesRead = 0
-  let wireTy = wireType(bytes[outOffset])
+
-  if wireTy != LengthDelimited:
+  checkType(bytes[outOffset], ty, outOffset)
-    raise newException(Exception, fmt"Not a length delimited value at offset {outOffset}! Received a {wireTy}")
 
   result.index = fieldNumber(bytes[outOffset])
   increaseBytesRead()
 
-  result.value = getLengthDelimited(bytes, ty, outOffset, outBytesProcessed, numBytesToRead)
+  result.value = bytes.get(ty, outOffset, outBytesProcessed, numBytesToRead)
 
-macro getField(obj: typed, fieldNum: int, ty: typedesc): untyped =
+proc decodeField*[T: object](
-  template fieldTypeCheck(obj, field, fieldNum, ty) =
+  bytes: var seq[byte],
-    when type(obj.field) is type(ty):
+  ty: typedesc[T],
-      obj.field
+  outOffset: var int,
-    else:
+  outBytesProcessed: var int,
-      let fnum {.inject.} = fieldNum
+  numBytesToRead = none(int)
-      raise newException(Exception, fmt"Could not find field at position {fnum}.")
+): ProtoField[T] {.inline.}
-
-  let typeFields = obj.getTypeInst.getType
-
-  let objFields = typeFields[2]
-  expectKind objFields, nnkRecList
-
-  result = newStmtList()
-  let caseStmt = newNimNode(nnkCaseStmt)
-  caseStmt.add(fieldNum)
-
-  for i in 0 ..< len(objFields) - 1:
-    let field = objFields[i]
-    let ofBranch = newNimNode(nnkOfBranch)
-    ofBranch.add(newLit(i+1))
-    ofBranch.add(getAst(fieldTypeCheck(obj, field, fieldNum, ty)))
-    caseStmt.add(ofBranch)
-
-  let field = objFields[len(objFields) - 1]
-  let elseBranch = newNimNode(nnkElse)
-  elseBranch.add(
-    nnkStmtList.newTree(getAst(fieldTypeCheck(obj, field, fieldNum, ty)))
-  )
-  caseStmt.add(elseBranch)
-
-  result.add(caseStmt)
 
 macro setField(obj: typed, fieldNum: int, offset: int, bytesProcessed: int, bytesToRead: Option[int], value: untyped): untyped =
   let typeFields = obj.getTypeInst.getType
@@ -367,7 +320,7 @@ proc decodeField*[T: object](
   # read LD header
   # then read only amount of bytes needed
   increaseBytesRead()
-  let decodedSize = getVarint(bytes, uint, outOffset, outBytesProcessed, numBytesToRead)
+  let decodedSize = bytes.get(uint, outOffset, outBytesProcessed, numBytesToRead)
   let bytesToRead = some(decodedSize.int)
 
   let oldOffset = outOffset