String buffer refactoring, part 2.

Switch to pointers for start/pos/end of buffer.
Abstract out some buffer writers.

1 files changed, 54 insertions, 10 deletions

diff --git a/src/lj_buf.c b/src/lj_buf.c
index 5d901d2a..a05dc22e 100644
--- a/src/lj_buf.c
+++ b/src/lj_buf.c
@@ -13,15 +13,20 @@
 #include "lj_err.h"
 #include "lj_buf.h"
 
-LJ_NOINLINE void lj_buf_grow(lua_State *L, SBuf *sb, MSize sz)
+LJ_NOINLINE void lj_buf_grow(lua_State *L, SBuf *sb, char *en)
 {
-  MSize bsz = sb->sz * 2;
+  char *b = sbufB(sb);
+  MSize sz = (MSize)(en - b);
+  MSize osz = (MSize)(sbufE(sb) - b), nsz = osz;
+  MSize n = (MSize)(sbufP(sb) - b);
   if (LJ_UNLIKELY(sz > LJ_MAX_MEM))
     lj_err_mem(L);
-  if (bsz < LJ_MIN_SBUF) bsz = LJ_MIN_SBUF;
-  while (bsz < sz) bsz += bsz;
-  sb->buf = lj_mem_realloc(L, sb->buf, sb->sz, bsz);
-  sb->sz = bsz;
+  if (nsz < LJ_MIN_SBUF) nsz = LJ_MIN_SBUF;
+  while (nsz < sz) nsz += nsz;
+  b = (char *)lj_mem_realloc(L, b, osz, nsz);
+  setmref(sb->b, b);
+  setmref(sb->p, b + n);
+  setmref(sb->e, b + nsz);
 }
 
 char *lj_buf_tmp(lua_State *L, MSize sz)
@@ -31,10 +36,49 @@ char *lj_buf_tmp(lua_State *L, MSize sz)
 
 void lj_buf_shrink(lua_State *L, SBuf *sb)
 {
-  MSize sz = sb->sz;
-  if (sz > 2*LJ_MIN_SBUF) {
-    sb->buf = lj_mem_realloc(L, sb->buf, sz, (sz >> 1));
-    sb->sz = (sz >> 1);
+  char *b = sbufB(sb);
+  MSize osz = (MSize)(sbufE(sb) - b);
+  if (osz > 2*LJ_MIN_SBUF) {
+    MSize n = (MSize)(sbufP(sb) - b);
+    b = lj_mem_realloc(L, b, osz, (osz >> 1));
+    setmref(sb->b, b);
+    setmref(sb->p, b + n);
+    setmref(sb->e, b + (osz >> 1));
   }
 }
 
+char *lj_buf_wmem(char *p, const void *q, MSize len)
+{
+  const char *s = (const char *)q, *e = s + len;
+  while (s < e) *p++ = *s++;
+  return p;
+}
+
+void lj_buf_putmem(lua_State *L, SBuf *sb, const void *q, MSize len)
+{
+  char *p = lj_buf_more(L, sb, len);
+  p = lj_buf_wmem(p, q, len);
+  setsbufP(sb, p);
+}
+
+uint32_t lj_buf_ruleb128(const char **pp)
+{
+  const uint8_t *p = (const uint8_t *)*pp;
+  uint32_t v = *p++;
+  if (LJ_UNLIKELY(v >= 0x80)) {
+    int sh = 0;
+    v &= 0x7f;
+    do { v |= ((*p & 0x7f) << (sh += 7)); } while (*p++ >= 0x80);
+  }
+  *pp = (const char *)p;
+  return v;
+}
+
+char *lj_buf_wuleb128(char *p, uint32_t v)
+{
+  for (; v >= 0x80; v >>= 7)
+    *p++ = (char)((v & 0x7f) | 0x80);
+  *p++ = (char)v;
+  return p;
+}
+