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Add optional root table to SetString and ResizeVector, when your Flatbuffer isn't the schema's root type. #237

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3 commits merged into from
Jul 22, 2015
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Add optional root table to SetString and ResizeVector, when your Flatbuffer isn't the schema's root type. #237

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a4de6de
Add optional root table name to SetString and ResizeVector.
jonsimantov Jul 22, 2015
6e160f4
Use Object* for optional root_table in SetString/ResizeVector.
jonsimantov Jul 22, 2015
b56020a
Updated pointer syntax to be consistent in SetString, etc.
jonsimantov Jul 22, 2015
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26 changes: 17 additions & 9 deletions include/flatbuffers/reflection.h
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Original file line number Diff line number Diff line change
Expand Up @@ -271,10 +271,13 @@ inline const reflection::Object &GetUnionType(
// "delta" may be negative (shrinking).
// Unless "delta" is a multiple of the largest alignment, you'll create a small
// amount of garbage space in the buffer (usually 0..7 bytes).
// If your FlatBuffer's root table is not the schema's root table, you should
// pass in your root_table type as well.
class ResizeContext {
public:
ResizeContext(const reflection::Schema &schema, uoffset_t start, int delta,
std::vector<uint8_t> *flatbuf)
std::vector<uint8_t> *flatbuf,
const reflection::Object *root_table = nullptr)
: schema_(schema), startptr_(flatbuf->data() + start),
delta_(delta), buf_(*flatbuf),
dag_check_(flatbuf->size() / sizeof(uoffset_t), false) {
Expand All @@ -284,7 +287,7 @@ class ResizeContext {
// Now change all the offsets by delta_.
auto root = GetAnyRoot(buf_.data());
Straddle<uoffset_t, 1>(buf_.data(), root, buf_.data());
ResizeTable(*schema.root_table(), root);
ResizeTable(root_table ? *root_table : *schema.root_table(), root);
// We can now add or remove bytes at start.
if (delta_ > 0) buf_.insert(buf_.begin() + start, delta_, 0);
else buf_.erase(buf_.begin() + start, buf_.begin() + start - delta_);
Expand Down Expand Up @@ -395,15 +398,18 @@ class ResizeContext {
// Changes the contents of a string inside a FlatBuffer. FlatBuffer must
// live inside a std::vector so we can resize the buffer if needed.
// "str" must live inside "flatbuf" and may be invalidated after this call.
// If your FlatBuffer's root table is not the schema's root table, you should
// pass in your root_table type as well.
inline void SetString(const reflection::Schema &schema, const std::string &val,
const String *str, std::vector<uint8_t> *flatbuf) {
const String *str, std::vector<uint8_t> *flatbuf,
const reflection::Object *root_table = nullptr) {
auto delta = static_cast<int>(val.size()) - static_cast<int>(str->Length());
auto start = static_cast<uoffset_t>(reinterpret_cast<const uint8_t *>(str) -
flatbuf->data() +
sizeof(uoffset_t));
if (delta) {
// Different size, we must expand (or contract).
ResizeContext(schema, start, delta, flatbuf);
ResizeContext(schema, start, delta, flatbuf, root_table);
if (delta < 0) {
// Clear the old string, since we don't want parts of it remaining.
memset(flatbuf->data() + start, 0, str->Length());
Expand All @@ -416,17 +422,19 @@ inline void SetString(const reflection::Schema &schema, const std::string &val,
// Resizes a flatbuffers::Vector inside a FlatBuffer. FlatBuffer must
// live inside a std::vector so we can resize the buffer if needed.
// "vec" must live inside "flatbuf" and may be invalidated after this call.
template<typename T> void ResizeVector(const reflection::Schema &schema,
uoffset_t newsize, T val,
const Vector<T> *vec,
std::vector<uint8_t> *flatbuf) {
// If your FlatBuffer's root table is not the schema's root table, you should
// pass in your root_table type as well.
template <typename T>
void ResizeVector(const reflection::Schema &schema, uoffset_t newsize, T val,
const Vector<T> *vec, std::vector<uint8_t> *flatbuf,
const reflection::Object *root_table = nullptr) {
auto delta_elem = static_cast<int>(newsize) - static_cast<int>(vec->size());
auto delta_bytes = delta_elem * static_cast<int>(sizeof(T));
auto vec_start = reinterpret_cast<const uint8_t *>(vec) - flatbuf->data();
auto start = static_cast<uoffset_t>(vec_start + sizeof(uoffset_t) +
sizeof(T) * vec->size());
if (delta_bytes) {
ResizeContext(schema, start, delta_bytes, flatbuf);
ResizeContext(schema, start, delta_bytes, flatbuf, root_table);
WriteScalar(flatbuf->data() + vec_start, newsize); // Length field.
// Set new elements to "val".
for (int i = 0; i < delta_elem; i++) {
Expand Down