Use strncpy instead of byte-oriented operations

The strncpy(s1, s2, n) function shall copy not more than n bytes
(bytes that follow a NUL character are not copied) from the array
pointed to by s2 to the array pointed to by s1. Both strncpy and strlen
are usually optimized in libc implementation, and we should utilize
them when possible.

Author: jserv

src/io.c

@@ -61,27 +61,22 @@ void memory_delete(memory_t *mem)
     free(mem);
 }
 
-void memory_read(memory_t *mem, uint8_t *dst, uint32_t addr, uint32_t size)
+void memory_read(const memory_t *mem,
+                 uint8_t *dst,
+                 uint32_t addr,
+                 uint32_t size)
 {
     memcpy(dst, mem->mem_base + addr, size);
 }
 
-uint32_t memory_read_str(memory_t *mem,
+uint32_t memory_read_str(const memory_t *mem,
                          uint8_t *dst,
                          uint32_t addr,
                          uint32_t max)
 {
-    uint32_t len = 0;
-    const uint8_t *end = dst + max;
-    for (;; ++len, ++dst) {
-        uint8_t ch = 0;
-        memory_read(mem, &ch, addr + len, 1);
-        if (dst < end)
-            *dst = ch;
-        if (!ch)
-            break;
-    }
-    return len + 1;
+    char *d = (char *) dst;
+    char *s = (char *) mem->mem_base + addr;
+    return strlen(strncpy(d, s, max));
 }
 
 uint32_t memory_ifetch(uint32_t addr)

src/io.h

@@ -21,7 +21,7 @@ memory_t *memory_new();
 void memory_delete(memory_t *m);
 
 /* read a C-style string from memory */
-uint32_t memory_read_str(memory_t *m,
+uint32_t memory_read_str(const memory_t *m,
                          uint8_t *dst,
                          uint32_t addr,
                          uint32_t max);
@@ -39,7 +39,7 @@ uint16_t memory_read_s(uint32_t addr);
 uint8_t memory_read_b(uint32_t addr);
 
 /* read a length of data from memory */
-void memory_read(memory_t *m, uint8_t *dst, uint32_t addr, uint32_t size);
+void memory_read(const memory_t *m, uint8_t *dst, uint32_t addr, uint32_t size);
 
 static inline void memory_write(memory_t *m,
                                 uint32_t addr,