Byte array (#1)

Reviewed-on: #1

src/bytecode/bytearray.cc

@@ -0,0 +1,84 @@
+#include "bytearray.hh"
+
+#include <cstring>
+
+namespace tyche {
+
+void ByteArray::add_byte(uint32_t addr, uint8_t byte)
+{
+    try {
+        data_.at(addr) = byte;
+    } catch (std::out_of_range&) {
+        data_.resize(addr + 1, 0);
+        data_.at(addr) = byte;
+    }
+}
+
+void ByteArray::add_int(uint32_t addr, int32_t value)
+{
+    uint32_t zz = ((uint32_t)(value << 1)) ^ ((uint32_t)(value >> 31));
+    while (zz > 0x7F) {
+        add_byte(addr++, (zz & 0x7F) | 0x80);
+        zz >>= 7;
+    }
+    add_byte(addr, zz & 0x7F);
+}
+
+void ByteArray::add_float(uint32_t addr, float value)
+{
+    uint32_t bits;
+    std::memcpy(&bits, &value, 4);
+    add_byte(addr, (uint8_t)(bits));
+    add_byte(addr+1, (uint8_t)(bits >> 8));
+    add_byte(addr+2, (uint8_t)(bits >> 16));
+    add_byte(addr+3, (uint8_t)(bits >> 24));
+}
+
+void ByteArray::add_string(uint32_t addr, std::string const& str)
+{
+    for (uint8_t c: str)
+        add_byte(addr++, c);
+    add_byte(addr, 0);
+}
+
+uint8_t ByteArray::get_byte(uint32_t addr) const
+{
+    return data_.at(addr);
+}
+
+std::pair<int32_t, size_t> ByteArray::get_int(uint32_t addr) const
+{
+    uint32_t zz = 0;
+    int shift = 0;
+    for (size_t i = 0; shift < 35; i++) {
+        uint8_t byte = get_byte(addr++);
+        zz |= (uint32_t)(byte & 0x7F) << shift;
+        if (!(byte & 0x80)) {
+            int32_t value = (int32_t)((zz >> 1) ^ -(zz & 1));
+            return std::make_pair(value, (int)(i + 1));
+        }
+        shift += 7;
+    }
+    throw BytecodeParsingError("Error parsing int32 at position " + std::to_string(addr));
+}
+
+std::pair<float, size_t> ByteArray::get_float(uint32_t addr) const
+{
+    uint32_t bits = (uint32_t) get_byte(addr)
+            | (uint32_t) get_byte(addr+1) << 8
+            | (uint32_t) get_byte(addr+2) << 16
+            | (uint32_t) get_byte(addr+3) << 24;
+    float value;
+    std::memcpy(&value, &bits, 4);
+    return { value, 4 };
+}
+
+std::pair<std::string, size_t> ByteArray::get_string(uint32_t addr) const
+{
+    std::string data;
+    while (char c = (char) get_byte(addr++))
+        data += c;
+    return { data, data.size() + 1 };
+}
+
+}