add StructLayout::convert (WIP)

src/data/StructLayout.cpp

@@ -2,7 +2,6 @@
 
 #include <cstring>
 #include <string.h>
-#include <stdexcept>
 #include <algorithm>
 
 #include "util/data_io.hpp"
@@ -36,6 +35,35 @@ StructLayout StructLayout::create(const std::vector<Field>& fields) {
         offset, std::move(builtFields), std::move(indices));
 }
 
+static inline constexpr bool is_integer_type(FieldType type) {
+    return (type >= FieldType::I8 && type <= FieldType::I64) || 
+            type == FieldType::CHAR;
+}
+
+static inline constexpr bool is_floating_point_type(FieldType type) {
+    return type == FieldType::F32 || type == FieldType::F64;
+}
+
+static inline constexpr bool is_numeric_type(FieldType type) {
+    return is_floating_point_type(type) || is_integer_type(type);
+}
+
+void StructLayout::convert(
+    const StructLayout& srcLayout, 
+    const ubyte* src, 
+    ubyte* dst,
+    bool allowDataLoss
+) const {
+    for (const Field& field : fields) {
+        auto srcField = srcLayout.getField(field.name);
+        if (srcField == nullptr) {
+            std::memset(dst + field.offset, 0, field.size);
+            continue;
+        }
+        // TODO: implement
+    }
+}
+
 const Field& StructLayout::requreField(const std::string& name) const {
     auto found = indices.find(name);
     if (found == indices.end()) {
@@ -54,7 +82,7 @@ static void set_int(ubyte* dst, integer_t value) {
 
 void StructLayout::setInteger(
     ubyte* dst, integer_t value, const std::string& name, int index
-) {
+) const {
     const auto& field = requreField(name);
     if (index < 0 || index >= field.elements) {
         throw std::out_of_range(
@@ -78,7 +106,7 @@ void StructLayout::setInteger(
 
 void StructLayout::setNumber(
     ubyte* dst, number_t value, const std::string& name, int index
-) {
+) const {
     const auto& field = requreField(name);
     if (index < 0 || index >= field.elements) {
         throw std::out_of_range(
@@ -107,7 +135,7 @@ void StructLayout::setNumber(
 
 size_t StructLayout::setChars(
     ubyte* dst, std::string_view value, const std::string& name
-) {
+) const {
     const auto& field = requreField(name);
     if (field.type != FieldType::CHAR) {
         throw std::runtime_error("'char' field type required");
@@ -120,7 +148,7 @@ size_t StructLayout::setChars(
 
 size_t StructLayout::setUnicode(
     ubyte* dst, std::string_view value, const std::string& name
-) {
+) const {
     const auto& field = requreField(name);
     if (field.type != FieldType::CHAR) {
         throw std::runtime_error("'char' field type required");

src/data/StructLayout.hpp

@@ -2,6 +2,7 @@
 
 #include <vector>
 #include <string>
+#include <stdexcept>
 #include <unordered_map>
 
 #include "typedefs.hpp"
@@ -19,6 +20,11 @@ namespace data {
         return sizes[static_cast<int>(type)];
     }
 
+    class dataloss_error : public std::runtime_error {
+    public:
+        dataloss_error(const std::string& message) : std::runtime_error(message) {}
+    };
+
     struct Field {
         FieldType type;
         std::string name;
@@ -99,7 +105,7 @@ namespace data {
         /// @param value value
         /// @param name field name
         /// @param index array index
-        void setInteger(ubyte* dst, integer_t value, const std::string& name, int index=0);
+        void setInteger(ubyte* dst, integer_t value, const std::string& name, int index=0) const;
 
         /// @brief Set field numeric value.
         /// Types: (f32, f64)
@@ -109,7 +115,7 @@ namespace data {
         /// @param value value
         /// @param name field name
         /// @param index array index
-        void setNumber(ubyte* dst, number_t value, const std::string& name, int index=0);
+        void setNumber(ubyte* dst, number_t value, const std::string& name, int index=0) const;
         
         /// @brief Replace chars array to given ASCII string
         /// @throws std::runtime_exception - field not found
@@ -118,7 +124,7 @@ namespace data {
         /// @param value ASCII string
         /// @param name field name
         /// @return number of written string chars
-        size_t setChars(ubyte* dst, std::string_view value, const std::string& name);
+        size_t setChars(ubyte* dst, std::string_view value, const std::string& name) const;
         
         /// @brief Unicode-safe version of setChars
         /// @throws std::runtime_exception - field not found
@@ -126,23 +132,31 @@ namespace data {
         /// @param value utf-8 string
         /// @param name field name
         /// @return number of written string chars
-        size_t setUnicode(ubyte* dst, std::string_view value, const std::string& name);
+        size_t setUnicode(ubyte* dst, std::string_view value, const std::string& name) const;
 
         /// @return total structure size (bytes)
         [[nodiscard]] size_t size() const {
             return totalSize;
         }
 
+        /// @brief Convert structure data from srcLayout to this layout.
+        /// @param srcLayout source structure layout
+        /// @param src source data
+        /// @param dst destination buffer
+        /// (size must be enough to store converted structure) 
+        /// @param allowDataLoss allow to drop fields that are not present in 
+        /// this layout or have incompatible types
+        /// @throws data::dataloss_error - data loss detected and allowDataLoss 
+        /// is set to false
+        void convert(
+            const StructLayout& srcLayout, 
+            const ubyte* src, 
+            ubyte* dst,
+            bool allowDataLoss) const;
+
+        /// TODO: add checkCompatibility method
+
         [[nodiscard]]
         static StructLayout create(const std::vector<Field>& fields);
     };
-
-    class StructAccess {
-        const StructLayout& mapping;
-        uint8_t* buffer;
-    public:
-        StructAccess(const StructLayout& mapping, uint8_t* buffer)
-            : mapping(mapping), buffer(buffer) {
-        }
-    };
 }

test/data/StructLayout.cpp

@@ -39,3 +39,7 @@ TEST(StructLayout, Unicode) {
      layout.setUnicode(buffer, u8"пример", "text");
      EXPECT_EQ(layout.getChars(buffer, "text"), std::string(u8"пр"));
 }
+
+TEST(StructLayout, Convert) {
+    
+}