From f2addcef0a610b9925d74c442ccf0c9ce68699e5 Mon Sep 17 00:00:00 2001
From: Aryadev Chavali <aryadev@aryadevchavali.com>
Date: Wed, 19 Jun 2024 20:26:30 +0100
Subject: [PATCH] Introducing short to data_t and handlers for converting
 endian

---
 lib/base.c | 21 +++++++++++++++++++++
 lib/base.h | 49 +++++++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 68 insertions(+), 2 deletions(-)

diff --git a/lib/base.c b/lib/base.c
index 486fa91..5fa5a04 100644
--- a/lib/base.c
+++ b/lib/base.c
@@ -14,6 +14,12 @@
 
 #include <string.h>
 
+short_t short_byteswap(const short_t w)
+{
+  // TODO: is there a faster way of doing this?
+  return WORD_NTH_BYTE(w, 1) | (WORD_NTH_BYTE(w, 0) << 8);
+}
+
 hword_t hword_byteswap(const hword_t w)
 {
   // TODO: is there a faster way of doing this?
@@ -30,6 +36,15 @@ word_t word_byteswap(const word_t w)
          WORD_NTH_BYTE(w, 1) << 48 | WORD_NTH_BYTE(w, 0) << 56;
 }
 
+short_t convert_bytes_to_short(const byte_t *bytes)
+{
+  short_t s = 0;
+  memcpy(&s, bytes, SHORT_SIZE);
+  if (!LITTLE_ENDIAN)
+    s = short_byteswap(s);
+  return s;
+}
+
 hword_t convert_bytes_to_hword(const byte_t *bytes)
 {
   hword_t h = 0;
@@ -48,6 +63,12 @@ word_t convert_bytes_to_word(const byte_t *bytes)
   return h;
 }
 
+void convert_short_to_bytes(short_t w, byte_t *bytes)
+{
+  short_t h = LITTLE_ENDIAN ? w : short_byteswap(w);
+  memcpy(bytes, &h, SHORT_SIZE);
+}
+
 void convert_hword_to_bytes(hword_t w, byte_t *bytes)
 {
   hword_t h = LITTLE_ENDIAN ? w : hword_byteswap(w);
diff --git a/lib/base.h b/lib/base.h
index da1d564..1c05a7d 100644
--- a/lib/base.h
+++ b/lib/base.h
@@ -35,22 +35,26 @@
 /* Ease of use aliases for numeric types */
 typedef uint8_t u8;
 typedef int8_t i8;
+typedef uint16_t u16;
+typedef int16_t i16;
 typedef uint32_t u32;
 typedef int32_t i32;
+typedef float f32;
 typedef uint64_t u64;
 typedef int64_t i64;
-
-typedef float f32;
 typedef double f64;
 
 typedef u8 byte_t;
 typedef i8 sbyte_t;
+typedef u16 short_t;
+typedef i16 sshort_t;
 typedef u32 hword_t;
 typedef i32 shword_t;
 typedef u64 word_t;
 typedef i64 sword_t;
 
 /* Macros for the sizes of common base data types. */
+#define SHORT_SIZE sizeof(short_t)
 #define HWORD_SIZE sizeof(hword_t)
 #define WORD_SIZE  sizeof(word_t)
 
@@ -74,6 +78,8 @@ typedef union
 {
   byte_t as_byte;
   sbyte_t as_sbyte;
+  short_t as_short;
+  sshort_t as_sshort;
   hword_t as_hword;
   shword_t as_shword;
   word_t as_word;
@@ -88,12 +94,14 @@ typedef enum
 {
   DATA_TYPE_NIL = -1,
   DATA_TYPE_BYTE,
+  DATA_TYPE_SHORT,
   DATA_TYPE_HWORD,
   DATA_TYPE_WORD,
 } data_type_t;
 
 /* Some macros for constructing data_t instances quickly. */
 #define DBYTE(BYTE)   ((data_t){.as_byte = (BYTE)})
+#define DSHORT(SHORT) ((data_t){.as_short = (SHORT)})
 #define DHWORD(HWORD) ((data_t){.as_hword = (HWORD)})
 #define DWORD(WORD)   ((data_t){.as_word = (WORD)})
 
@@ -119,6 +127,13 @@ static const hword_t __i = 0xFFFF0000;
 */
 #define WORD_NTH_BYTE(WORD, N) (((WORD) >> ((N) * 8)) & 0xFF)
 
+/**
+   @brief Return the Nth short of WORD.
+
+   @details N should range from 0 to 3 as there are 4 shorts in a word
+*/
+#define WORD_NTH_SHORT(WORD, N) (((WORD) >> ((N) * 16)) & 0xFFFF)
+
 /**
    @brief Return the Nth half word of WORD.
 
@@ -127,6 +142,26 @@ static const hword_t __i = 0xFFFF0000;
 */
 #define WORD_NTH_HWORD(WORD, N) (((WORD) >> ((N) * 32)) & 0xFFFFFFFF)
 
+/**
+   @brief Convert a buffer of bytes to a short
+
+   @details It is assumed that the buffer of bytes are in virtual
+   machine byte code format (little endian) and that they are at least
+   SHORT_SIZE in size.
+ */
+short_t convert_bytes_to_short(const byte_t *buffer);
+
+/**
+   @brief Convert a half word into a VM byte code format bytes (big
+   endian)
+
+   @param s: Short to convert
+
+   @param buffer: Buffer to store into.  It is assumed that the buffer
+   has at least SHORT_SIZE space.
+*/
+void convert_short_to_bytes(const short_t s, byte_t *buffer);
+
 /**
    @brief Convert a buffer of bytes to a half word.
 
@@ -167,6 +202,16 @@ word_t convert_bytes_to_word(const byte_t *);
 */
 void convert_word_to_bytes(const word_t w, byte_t *buffer);
 
+/**
+   @brief Swap the ordering of bytes within an short
+
+   @details The ordering of the bytes in the short are reversed (2
+   bytes in a short).
+
+   @param s: short to swap
+ */
+short_t short_byteswap(const short_t s);
+
 /**
    @brief Swap the ordering of bytes within an half word