C bindings: Implement _Validate(), and some pre-requisites

mojo/public/c/bindings/lib/type_descriptor.c

Index: mojo/public/c/bindings/lib/type_descriptor.c
diff --git a/mojo/public/c/bindings/lib/type_descriptor.c b/mojo/public/c/bindings/lib/type_descriptor.c
index 3e23011dc325f57caf6c1a1664d321d2d6308dfa..2846965b02ee033f267a1463a89ff4fbd5702065 100644
--- a/mojo/public/c/bindings/lib/type_descriptor.c
+++ b/mojo/public/c/bindings/lib/type_descriptor.c
@@ -7,10 +7,11 @@
 #include <assert.h>
 
 #include "mojo/public/c/bindings/array.h"
+#include "mojo/public/c/bindings/interface.h"
 #include "mojo/public/c/bindings/lib/util.h"
+#include "mojo/public/c/bindings/map.h"
 #include "mojo/public/c/bindings/struct.h"
 #include "mojo/public/c/bindings/union.h"
-#include "mojo/public/c/bindings/interface.h"
 
 const struct MojomTypeDescriptorArray g_mojom_string_type_description = {
     MOJOM_TYPE_DESCRIPTOR_TYPE_POD,  // elem_type
@@ -25,9 +26,10 @@ const struct MojomTypeDescriptorArray g_mojom_string_type_description = {
 static const MojoHandle kEncodedHandleInvalid = (MojoHandle)-1;
 
 bool MojomType_IsPointer(enum MojomTypeDescriptorType type) {
- return type == MOJOM_TYPE_DESCRIPTOR_TYPE_STRUCT_PTR ||
-        type == MOJOM_TYPE_DESCRIPTOR_TYPE_ARRAY_PTR ||
-        type == MOJOM_TYPE_DESCRIPTOR_TYPE_UNION_PTR;
+  return type == MOJOM_TYPE_DESCRIPTOR_TYPE_STRUCT_PTR ||
+         type == MOJOM_TYPE_DESCRIPTOR_TYPE_MAP_PTR ||
+         type == MOJOM_TYPE_DESCRIPTOR_TYPE_ARRAY_PTR ||
+         type == MOJOM_TYPE_DESCRIPTOR_TYPE_UNION_PTR;
 }
 
 size_t MojomType_DispatchComputeSerializedSize(
@@ -38,6 +40,7 @@ size_t MojomType_DispatchComputeSerializedSize(
   const void* data_ptr = data;
   size_t size = 0;
   switch (type) {
+    case MOJOM_TYPE_DESCRIPTOR_TYPE_MAP_PTR:
     case MOJOM_TYPE_DESCRIPTOR_TYPE_STRUCT_PTR: {
       data_ptr = ((const union MojomPointer*)data_ptr)->ptr;
       if (!nullable || data_ptr != NULL)
@@ -140,6 +143,7 @@ void MojomType_DispatchEncodePointersAndHandles(
 
   void* union_buf = inout_buf;
   switch (in_elem_type) {
+    case MOJOM_TYPE_DESCRIPTOR_TYPE_MAP_PTR:
     case MOJOM_TYPE_DESCRIPTOR_TYPE_STRUCT_PTR: {
       struct MojomStructHeader* inout_struct =
           ((union MojomPointer*)inout_buf)->ptr;
@@ -205,6 +209,7 @@ void MojomType_DispatchDecodePointersAndHandles(
 
   void* union_buf = inout_buf;
   switch (in_elem_type) {
+    case MOJOM_TYPE_DESCRIPTOR_TYPE_MAP_PTR:
     case MOJOM_TYPE_DESCRIPTOR_TYPE_STRUCT_PTR: {
       decode_pointer(inout_buf);
       struct MojomStructHeader* inout_struct =
@@ -268,3 +273,129 @@ void MojomType_DispatchDecodePointersAndHandles(
       break;
   }
 }
+
+// Validates that the offset (|pointer->offset|) points to a new memory region,
+// i.e. one that hasn't been referenced yet. If so, moves the expected offset
+// (for the next pointer) forward.
+static MojomValidationResult validate_pointer(
+    const union MojomPointer* pointer,
+    size_t max_offset,
+    bool is_nullable,
+    struct MojomValidationContext* inout_context) {
+  // Offset must be <= UINT32_MAX and within range.
+  if (pointer->offset > max_offset || pointer->offset > UINT32_MAX)
+    return MOJOM_VALIDATION_ILLEGAL_POINTER;
+
+  if (pointer->offset != 0) {
+    if ((char*)pointer + pointer->offset < inout_context->next_pointer)
+      return MOJOM_VALIDATION_ILLEGAL_MEMORY_RANGE;
+
+    inout_context->next_pointer = (char*)pointer + pointer->offset;
+  }
+
+  // Offset must be 8-byte aligned: this check is sufficient, given that all
+  // objects are rounded to 8-bytes.
+  if ((pointer->offset & 7) != 0)
+    return MOJOM_VALIDATION_MISALIGNED_OBJECT;
+
+  if (!is_nullable && pointer->offset == 0)
+    return MOJOM_VALIDATION_UNEXPECTED_NULL_POINTER;
+
+  return MOJOM_VALIDATION_ERROR_NONE;
+}
+
+static MojomValidationResult validate_handle(
+    MojoHandle encoded_handle, uint32_t num_handles, bool is_nullable,
+    struct MojomValidationContext* inout_context) {
+  if (!is_nullable && encoded_handle == kEncodedHandleInvalid)
+    return MOJOM_VALIDATION_UNEXPECTED_INVALID_HANDLE;
+
+  if (encoded_handle != kEncodedHandleInvalid) {
+    if (encoded_handle >= num_handles ||
+        encoded_handle < inout_context->next_handle_index)
+      return MOJOM_VALIDATION_ILLEGAL_HANDLE;
+
+    inout_context->next_handle_index = encoded_handle + 1;
+  }
+
+  return MOJOM_VALIDATION_ERROR_NONE;
+}
+
+MojomValidationResult MojomType_DispatchValidate(
+    enum MojomTypeDescriptorType in_elem_type, const void* in_type_desc,
+    bool in_nullable, const void* in_buf, uint32_t in_buf_size,
+    uint32_t in_num_handles, struct MojomValidationContext* inout_context) {
+  assert(in_buf);
+
+  struct MojomUnionLayout* union_data = (struct MojomUnionLayout*)in_buf;
+  switch (in_elem_type) {
+    case MOJOM_TYPE_DESCRIPTOR_TYPE_MAP_PTR:
+    case MOJOM_TYPE_DESCRIPTOR_TYPE_STRUCT_PTR: {
+      union MojomPointer* pointer = (union MojomPointer*)in_buf;
+      MojomValidationResult result =
+          validate_pointer(pointer, in_buf_size, in_nullable, inout_context);
+      if (result != MOJOM_VALIDATION_ERROR_NONE || pointer->offset == 0)
+        return result;
+
+      result = MojomStruct_Validate(
+          (const struct MojomTypeDescriptorStruct*)in_type_desc,
+          (const struct MojomStructHeader*)((char*)in_buf + pointer->offset),
+          in_buf_size - pointer->offset, in_num_handles, inout_context);
+
+      if (result == MOJOM_VALIDATION_ERROR_NONE &&
+          in_elem_type == MOJOM_TYPE_DESCRIPTOR_TYPE_MAP_PTR) {
+        return MojomMap_Validate(
+            (const struct MojomTypeDescriptorStruct*)in_type_desc,
+            (const struct MojomStructHeader*)((char*)in_buf + pointer->offset),
+            in_buf_size - pointer->offset, in_num_handles, inout_context);
+      }
+
+      return result;
+    }
+    case MOJOM_TYPE_DESCRIPTOR_TYPE_ARRAY_PTR: {
+      union MojomPointer* pointer = (union MojomPointer*)in_buf;
+      MojomValidationResult result =
+          validate_pointer(pointer, in_buf_size, in_nullable, inout_context);
+      if (result != MOJOM_VALIDATION_ERROR_NONE || pointer->offset == 0)
+        return result;
+
+      return MojomArray_Validate(
+          (const struct MojomTypeDescriptorArray*)in_type_desc,
+          (const struct MojomArrayHeader*)((char*)in_buf + pointer->offset),
+          in_buf_size - pointer->offset, in_num_handles, inout_context);
+    }
+    case MOJOM_TYPE_DESCRIPTOR_TYPE_UNION_PTR: {
+      union MojomPointer* pointer = (union MojomPointer*)in_buf;
+      MojomValidationResult result =
+          validate_pointer(pointer, in_buf_size, in_nullable, inout_context);
+      if (result != MOJOM_VALIDATION_ERROR_NONE || pointer->offset == 0)
+        return result;
+
+      // Since this union is a pointer, we update |next_pointer| to be past the
+      // union data.
+      inout_context->next_pointer += sizeof(struct MojomUnionLayout);
+
+      union_data = (struct MojomUnionLayout*)((char*)in_buf + pointer->offset);
+      // Fall through.
+    }
+    case MOJOM_TYPE_DESCRIPTOR_TYPE_UNION:
+      if (union_data->size == 0) {
+        return in_nullable ? MOJOM_VALIDATION_ERROR_NONE
+                           : MOJOM_VALIDATION_UNEXPECTED_NULL_UNION;
+      }
+
+      return MojomUnion_Validate(
+          (const struct MojomTypeDescriptorUnion*)in_type_desc, in_nullable,
+          union_data, in_buf_size - ((char*)union_data - (char*)in_buf),
+          in_num_handles, inout_context);
+    case MOJOM_TYPE_DESCRIPTOR_TYPE_HANDLE:
+      return validate_handle(*(const MojoHandle*)in_buf, in_num_handles,
+                             in_nullable, inout_context);
+    case MOJOM_TYPE_DESCRIPTOR_TYPE_INTERFACE:
+      return validate_handle(((const struct MojomInterfaceData*)in_buf)->handle,
+                             in_num_handles, in_nullable, inout_context);
+    case MOJOM_TYPE_DESCRIPTOR_TYPE_POD:
+      break;
+  }
+  return MOJOM_VALIDATION_ERROR_NONE;
+}