bpo-40313: speed up bytes.hex() (GH-19594)
Automerge-Triggered-By: @gpshead
diff --git a/Misc/NEWS.d/next/Core and Builtins/2020-04-20-23-58-35.bpo-40313.USVRW8.rst b/Misc/NEWS.d/next/Core and Builtins/2020-04-20-23-58-35.bpo-40313.USVRW8.rst
new file mode 100644
index 0000000..52880ab
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2020-04-20-23-58-35.bpo-40313.USVRW8.rst
@@ -0,0 +1 @@
+Improve the performance of bytes.hex().
\ No newline at end of file
diff --git a/Python/pystrhex.c b/Python/pystrhex.c
index 7e4fad3..b74e57a 100644
--- a/Python/pystrhex.c
+++ b/Python/pystrhex.c
@@ -82,22 +82,59 @@
/* Hexlify */
Py_ssize_t i, j;
- for (i=j=0; i < arglen; ++i) {
- assert((j + 1) < resultlen);
- unsigned char c;
- c = (argbuf[i] >> 4) & 0x0f;
- retbuf[j++] = Py_hexdigits[c];
- c = argbuf[i] & 0x0f;
- retbuf[j++] = Py_hexdigits[c];
- if (bytes_per_sep_group && i < arglen - 1) {
- Py_ssize_t anchor;
- anchor = (bytes_per_sep_group > 0) ? (arglen - 1 - i) : (i + 1);
- if (anchor % abs_bytes_per_sep == 0) {
+ unsigned char c;
+
+ if (bytes_per_sep_group == 0) {
+ for (i = j = 0; i < arglen; ++i) {
+ assert((j + 1) < resultlen);
+ c = argbuf[i];
+ retbuf[j++] = Py_hexdigits[c >> 4];
+ retbuf[j++] = Py_hexdigits[c & 0x0f];
+ }
+ assert(j == resultlen);
+ }
+ else {
+ /* The number of complete chunk+sep periods */
+ Py_ssize_t chunks = (arglen - 1) / abs_bytes_per_sep;
+ Py_ssize_t chunk;
+ unsigned int k;
+
+ if (bytes_per_sep_group < 0) {
+ i = j = 0;
+ for (chunk = 0; chunk < chunks; chunk++) {
+ for (k = 0; k < abs_bytes_per_sep; k++) {
+ c = argbuf[i++];
+ retbuf[j++] = Py_hexdigits[c >> 4];
+ retbuf[j++] = Py_hexdigits[c & 0x0f];
+ }
retbuf[j++] = sep_char;
}
+ while (i < arglen) {
+ c = argbuf[i++];
+ retbuf[j++] = Py_hexdigits[c >> 4];
+ retbuf[j++] = Py_hexdigits[c & 0x0f];
+ }
+ assert(j == resultlen);
+ }
+ else {
+ i = arglen - 1;
+ j = resultlen - 1;
+ for (chunk = 0; chunk < chunks; chunk++) {
+ for (k = 0; k < abs_bytes_per_sep; k++) {
+ c = argbuf[i--];
+ retbuf[j--] = Py_hexdigits[c & 0x0f];
+ retbuf[j--] = Py_hexdigits[c >> 4];
+ }
+ retbuf[j--] = sep_char;
+ }
+ while (i >= 0) {
+ c = argbuf[i--];
+ retbuf[j--] = Py_hexdigits[c & 0x0f];
+ retbuf[j--] = Py_hexdigits[c >> 4];
+ }
+ assert(j == -1);
}
}
- assert(j == resultlen);
#ifdef Py_DEBUG
if (!return_bytes) {