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Support for string_view slots #17

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Support for string_view slots #17

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4 changes: 4 additions & 0 deletions include/wrenbind17/any.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -199,6 +199,10 @@ namespace wrenbind17 {
return type == WREN_TYPE_STRING;
}

template <> inline bool ReturnValue::is<std::string_view>() const {
return type == WREN_TYPE_STRING;
}

template <> inline std::nullptr_t ReturnValue::as<std::nullptr_t>() {
if (!is<std::nullptr_t>()) {
throw BadCast("Return value is not a null");
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5 changes: 5 additions & 0 deletions include/wrenbind17/caller.hpp
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Expand Up @@ -74,6 +74,11 @@ namespace wrenbind17 {
}
};

template <>
inline void ForeginMethodReturnHelper<std::string_view>::push(WrenVM* vm, int index, std::string_view ret) {
PushHelper<std::string_view>::f(vm, index, ret);
}

template <>
inline void ForeginMethodReturnHelper<const std::string&>::push(WrenVM* vm, int index, const std::string& ret) {
PushHelper<const std::string&>::f(vm, index, ret);
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10 changes: 10 additions & 0 deletions include/wrenbind17/pop.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
#include <wren.hpp>

#include <string>
#include <string_view>
#include <memory>

#include "object.hpp"
Expand Down Expand Up @@ -54,6 +55,10 @@ namespace wrenbind17 {
return wrenGetSlotType(vm, idx) == WrenType::WREN_TYPE_STRING;
}

template <> inline bool is<std::string_view>(WrenVM* vm, const int idx) {
return wrenGetSlotType(vm, idx) == WrenType::WREN_TYPE_STRING;
}

template <> inline bool is<std::nullptr_t>(WrenVM* vm, const int idx) {
return wrenGetSlotType(vm, idx) == WrenType::WREN_TYPE_NULL;
}
Expand Down Expand Up @@ -255,6 +260,11 @@ namespace wrenbind17 {
return std::string(wrenGetSlotString(vm, idx));
}

template <> inline std::string_view getSlot(WrenVM* vm, int idx) {
validate<WrenType::WREN_TYPE_STRING>(vm, idx);
return std::string_view(wrenGetSlotString(vm, idx));
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This may be very dangerous. The string_view would not own the memory.

Therefore, if you have a C++ function that accepts string_view, and stores the string_view for a future use, then that may cause a segmentation fault. As far as I know Wren only guarantees that the raw bytes of that slot (string) is valid only during the call of the C++ function. The garbage collection may run after calling the function and the string_view points to an unknown memory.

This is fine the other way around. Wren makes a copy of the string/string_view you give it.

I am fine with accepting the risk, but could you update the documentation here? -> https://github.com/matusnovak/wrenbind17/blob/master/docs/content/Tutorial/types.md Maybe adding some section explaining this danger. I don't mind the exact paragraphs, I can leave that to you. Plus a brief comment on this line that yes it is a risk.

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Sorry for the late response, but i got distracted with other projects and completly forgot about this PR, until i checked out my old project.

I can update the paragraph, but i think std::string_view does never own memory does it?
So the risk should probably be known to the user.

}

template <> inline std::nullptr_t getSlot(WrenVM* vm, int idx) {
validate<WrenType::WREN_TYPE_NULL>(vm, idx);
return nullptr;
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7 changes: 7 additions & 0 deletions include/wrenbind17/push.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
#include <wren.hpp>

#include <string>
#include <string_view>

#include "exception.hpp"
#include "object.hpp"
Expand Down Expand Up @@ -199,6 +200,12 @@ namespace wrenbind17 {
}
};

template <> struct PushHelper<std::string_view> {
static inline void f(WrenVM* vm, int idx, std::string_view value) {
wrenSetSlotString(vm, idx, value.data());
}
};

template <> struct PushHelper<const std::string> {
static inline void f(WrenVM* vm, int idx, const std::string value) {
wrenSetSlotString(vm, idx, value.c_str());
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