py: Change vstr so that it doesn't null terminate buffer by default.
This cleans up vstr so that it's a pure "variable buffer", and the user
can decide whether they need to add a terminating null byte. In most
places where vstr is used, the vstr did not need to be null terminated
and so this patch saves code size, a tiny bit of RAM, and makes vstr
usage more efficient. When null termination is needed it must be
done explicitly using vstr_null_terminate.
diff --git a/py/vstr.c b/py/vstr.c
index e71a6b7..ccd54d5 100644
--- a/py/vstr.c
+++ b/py/vstr.c
@@ -35,12 +35,10 @@
// returned value is always at least 1 greater than argument
#define ROUND_ALLOC(a) (((a) & ((~0) - 7)) + 8)
-// Init the vstr so it allocs exactly given number of bytes.
-// Length is set to zero, and null byte written in first position.
+// Init the vstr so it allocs exactly given number of bytes. Set length to zero.
void vstr_init(vstr_t *vstr, size_t alloc) {
- if (alloc < 2) {
- // need at least 1 byte for the null byte at the end
- alloc = 2;
+ if (alloc < 1) {
+ alloc = 1;
}
vstr->alloc = alloc;
vstr->len = 0;
@@ -49,24 +47,20 @@
vstr->had_error = true;
return;
}
- vstr->buf[0] = 0;
vstr->had_error = false;
vstr->fixed_buf = false;
}
-// Init the vstr so it allocs exactly enough ram to hold given length (plus the
-// null terminating byte), set the length, and write the null byte at the end.
+// Init the vstr so it allocs exactly enough ram to hold given length, and set the length.
void vstr_init_len(vstr_t *vstr, size_t len) {
- vstr_init(vstr, len + 1);
- vstr_add_len(vstr, len);
+ vstr_init(vstr, len);
+ vstr->len = len;
}
void vstr_init_fixed_buf(vstr_t *vstr, size_t alloc, char *buf) {
- assert(alloc > 0); // need at least room for the null byte
vstr->alloc = alloc;
vstr->len = 0;
vstr->buf = buf;
- vstr->buf[0] = 0;
vstr->had_error = false;
vstr->fixed_buf = true;
}
@@ -79,16 +73,16 @@
}
vstr_t *vstr_new(void) {
- vstr_t *vstr = m_new(vstr_t, 1);
+ vstr_t *vstr = m_new_obj(vstr_t);
if (vstr == NULL) {
return NULL;
}
- vstr_init(vstr, 32);
+ vstr_init(vstr, 16);
return vstr;
}
vstr_t *vstr_new_size(size_t alloc) {
- vstr_t *vstr = m_new(vstr_t, 1);
+ vstr_t *vstr = m_new_obj(vstr_t);
if (vstr == NULL) {
return NULL;
}
@@ -107,7 +101,6 @@
void vstr_reset(vstr_t *vstr) {
vstr->len = 0;
- vstr->buf[0] = 0;
vstr->had_error = false;
}
@@ -129,7 +122,7 @@
return vstr->len;
}
-// Extend vstr strictly by requested size, return pointer to newly added chunk
+// Extend vstr strictly by requested size, return pointer to newly added chunk.
char *vstr_extend(vstr_t *vstr, size_t size) {
if (vstr->fixed_buf) {
return NULL;
@@ -146,11 +139,11 @@
}
STATIC bool vstr_ensure_extra(vstr_t *vstr, size_t size) {
- if (vstr->len + size + 1 > vstr->alloc) {
+ if (vstr->len + size > vstr->alloc) {
if (vstr->fixed_buf) {
return false;
}
- size_t new_alloc = ROUND_ALLOC((vstr->len + size + 1) * 2);
+ size_t new_alloc = ROUND_ALLOC((vstr->len + size) * 2);
char *new_buf = m_renew(char, vstr->buf, vstr->alloc, new_alloc);
if (new_buf == NULL) {
vstr->had_error = true;
@@ -175,10 +168,17 @@
}
char *buf = vstr->buf + vstr->len;
vstr->len += len;
- vstr->buf[vstr->len] = 0;
return buf;
}
+// Doesn't increase len, just makes sure there is a null byte at the end
+void vstr_null_terminate(vstr_t *vstr) {
+ if (vstr->had_error || !vstr_ensure_extra(vstr, 1)) {
+ return;
+ }
+ vstr->buf[vstr->len] = '\0';
+}
+
void vstr_add_byte(vstr_t *vstr, byte b) {
byte *buf = (byte*)vstr_add_len(vstr, 1);
if (buf == NULL) {
@@ -224,11 +224,7 @@
buf[3] = (c & 0x3F) | 0x80;
}
#else
- byte *buf = (byte*)vstr_add_len(vstr, 1);
- if (buf == NULL) {
- return;
- }
- buf[0] = c;
+ vstr_add_byte(vstr, c);
#endif
}
@@ -239,7 +235,7 @@
void vstr_add_strn(vstr_t *vstr, const char *str, size_t len) {
if (vstr->had_error || !vstr_ensure_extra(vstr, len)) {
// if buf is fixed, we got here because there isn't enough room left
- // so just try to copy as much as we can, with room for null byte
+ // so just try to copy as much as we can, with room for a possible null byte
if (vstr->fixed_buf && vstr->len + 1 < vstr->alloc) {
len = vstr->alloc - vstr->len - 1;
goto copy;
@@ -249,7 +245,6 @@
copy:
memmove(vstr->buf + vstr->len, str, len);
vstr->len += len;
- vstr->buf[vstr->len] = 0;
}
STATIC char *vstr_ins_blank_bytes(vstr_t *vstr, size_t byte_pos, size_t byte_len) {
@@ -265,8 +260,8 @@
if (!vstr_ensure_extra(vstr, byte_len)) {
return NULL;
}
- // copy up the string to make room for the new bytes; +1 for the null byte
- memmove(vstr->buf + byte_pos + byte_len, vstr->buf + byte_pos, l - byte_pos + 1);
+ // copy up the string to make room for the new bytes
+ memmove(vstr->buf + byte_pos + byte_len, vstr->buf + byte_pos, l - byte_pos);
// increase the length
vstr->len += byte_len;
}
@@ -301,7 +296,6 @@
} else {
vstr->len -= len;
}
- vstr->buf[vstr->len] = 0;
}
void vstr_cut_out_bytes(vstr_t *vstr, size_t byte_pos, size_t bytes_to_cut) {
@@ -309,10 +303,8 @@
return;
} else if (byte_pos + bytes_to_cut >= vstr->len) {
vstr->len = byte_pos;
- vstr->buf[vstr->len] = 0;
} else {
- // move includes +1 for null byte at the end
- memmove(vstr->buf + byte_pos, vstr->buf + byte_pos + bytes_to_cut, vstr->len - byte_pos - bytes_to_cut + 1);
+ memmove(vstr->buf + byte_pos, vstr->buf + byte_pos + bytes_to_cut, vstr->len - byte_pos - bytes_to_cut);
vstr->len -= bytes_to_cut;
}
}