add new Bytearray class

res/modules/internal/bytearray.lua

@@ -0,0 +1,141 @@
+local MIN_CAPACITY = 8
+local _type = type
+local FFI = ffi
+
+FFI.cdef[[
+    void* malloc(size_t);
+    void free(void*);
+    typedef struct {
+        unsigned char* bytes;
+        int size;
+        int capacity;
+    } bytearray_t;
+]]
+
+local malloc = FFI.C.malloc
+local free = FFI.C.free
+
+local function grow_buffer(self, elems)
+    local new_capacity = math.ceil(self.capacity / 0.75 + elems)
+    local prev = self.bytes
+    self.bytes = malloc(new_capacity)
+    FFI.copy(self.bytes, prev, self.size)
+    self.capacity = new_capacity
+    free(prev)
+end
+
+local function count_elements(b)
+    local elems = 1
+    if _type(b) ~= "number" then
+        elems = #b
+    end
+    return elems
+end
+
+local bytearray_methods = {
+    append=function(self, b)
+        local elems = count_elements(b)
+        if self.size + elems > self.capacity then
+            grow_buffer(self, elems)
+        end
+        if _type(b) == "number" then
+            self.bytes[self.size] = b
+        else
+            for i=1, #b do
+                self.bytes[self.size + i - 1] = b[i]
+            end
+        end
+        self.size = self.size + elems
+    end,
+    insert=function(self, index, b)
+        local elems = count_elements(b)
+        if self.size + elems >= self.capacity then
+            grow_buffer(self, elems)
+        end
+        if _type(b) == "number" then
+            self.bytes[index] = b
+        else
+            for i=1, #b do
+                self.bytes[index + i - 1] = b[i]
+            end
+        end
+        self.size = self.size + elems
+    end,
+    remove=function(self, index, elems)
+        if index <= 0 or index > self.size then
+            return
+        end
+        if elems == nil then
+            elems = 1
+        end
+        if index + elems > self.size then
+            elems = self.size - index + 1
+        end
+        for i=index, self.size - elems do
+            self.bytes[i] = self.bytes[i + elems]
+        end
+        self.size = self.size - elems
+    end,
+    clear=function(self)
+        self.size = 0
+    end,
+    reserve=function(self, new_capacity)
+        if new_capacity <= self.capacity then
+            return
+        end
+        local prev = self.bytes
+        self.bytes = malloc(new_capacity)
+        FFI.copy(self.bytes, prev, self.size)
+        self.capacity = new_capacity
+        free(prev)
+    end,
+}
+
+local bytearray_mt = {
+    __index = function(self, key)
+        if _type(key) == "string" then
+            return bytearray_methods[key]
+        end
+        if key <= 0 or key > self.size then
+            return
+        end
+        return self.bytes[key - 1]
+    end,
+    __newindex = function(self, key, value)
+        if key <= 0 or key > self.size then
+            return
+        end
+        self.bytes[key - 1] = value
+    end,
+    __tostring = function(self)
+        return string.format("FFIBytearray[%s]{...}", tonumber(self.size))
+    end,
+    __len = function(self)
+        return tonumber(self.size)
+    end,
+    __gc = function(self)
+        free(self.bytes)
+    end
+}
+
+local utf8tostring = utf8.tostring
+
+function utf8.tostring(bytes)
+    local type = _type(bytes)
+    if type == "cdata" then
+        return FFI.string(bytes.bytes, bytes.size)
+    else
+        return utf8tostring(bytes)
+    end
+end
+
+local bytearray_type = FFI.metatype("bytearray_t", bytearray_mt)
+
+return function (n)
+    n = n or 0
+    if n < MIN_CAPACITY then
+        return bytearray_type(malloc(MIN_CAPACITY), n, MIN_CAPACITY)
+    else
+        return bytearray_type(malloc(n), n, n)
+    end
+end