initial work for integer encoding in ziplists

diff --git a/zip.c b/zip.c
index cef7b1a32aa76ed1e16801f23a2857987dd88e62..e8f01edb74267e230a70959b521aa624a118624c 100644 (file)
--- a/zip.c
+++ b/zip.c
@@ -1,41 +1,153 @@
 #define ZIP_BIGLEN 254
 #define ZIP_END 255
 
-/* The following macro returns the number of bytes needed to encode the length
- * for the integer value _l, that is, 1 byte for lengths < ZIP_BIGLEN and
- * 5 bytes for all the other lengths. */
-#define ZIP_LEN_BYTES(_l) (((_l) < ZIP_BIGLEN) ? 1 : sizeof(unsigned int)+1)
+/* Entry encoding */
+#define ZIP_ENC_RAW     0
+#define ZIP_ENC_SHORT   1
+#define ZIP_ENC_INT     2
+#define ZIP_ENC_LLONG   3
+#define ZIP_ENCODING(p) ((p)[0] >> 6)
 
-/* Decode the encoded length pointed by 'p' */
-static unsigned int zipDecodeLength(unsigned char *p) {
-    unsigned int len = *p;
+/* Length encoding for raw entries */
+#define ZIP_LEN_INLINE  0
+#define ZIP_LEN_UINT16  1
+#define ZIP_LEN_UINT32  2
 
-    if (len < ZIP_BIGLEN) return len;
-    memcpy(&len,p+1,sizeof(unsigned int));
+static unsigned int zipEncodingSize(char encoding) {
+    if (encoding == ZIP_ENC_SHORT) {
+        return sizeof(short int);
+    } else if (encoding == ZIP_ENC_INT) {
+        return sizeof(int);
+    } else if (encoding == ZIP_ENC_LLONG) {
+        return sizeof(long long);
+    }
+    assert(NULL);
+}
+
+/* Decode the encoded length pointed by 'p'. If a pointer to 'lensize' is
+ * provided, it is set to the number of bytes required to encode the length. */
+static unsigned int zipDecodeLength(unsigned char *p, unsigned int *lensize) {
+    unsigned char encoding = ZIP_ENCODING(p), lenenc;
+    unsigned int len;
+
+    if (encoding == ZIP_ENC_RAW) {
+        lenenc = (p[0] >> 4) & 0x3;
+        if (lenenc == ZIP_LEN_INLINE) {
+            len = p[0] & 0xf;
+            if (lensize) *lensize = 1;
+        } else if (lenenc == ZIP_LEN_UINT16) {
+            len = p[1] | (p[2] << 8);
+            if (lensize) *lensize = 3;
+        } else {
+            len = p[1] | (p[2] << 8) | (p[3] << 16) | (p[4] << 24);
+            if (lensize) *lensize = 5;
+        }
+    } else {
+        len = zipEncodingSize(encoding);
+        if (lensize) *lensize = 1;
+    }
     return len;
 }
 
 /* Encode the length 'l' writing it in 'p'. If p is NULL it just returns
  * the amount of bytes required to encode such a length. */
-static unsigned int zipEncodeLength(unsigned char *p, unsigned int len) {
-    if (p == NULL) {
-        return ZIP_LEN_BYTES(len);
-    } else {
-        if (len < ZIP_BIGLEN) {
-            p[0] = len;
-            return 1;
+static unsigned int zipEncodeLength(unsigned char *p, char encoding, unsigned int rawlen) {
+    unsigned char len = 1, lenenc, buf[5];
+    if (encoding == ZIP_ENC_RAW) {
+        if (rawlen <= 0xf) {
+            if (!p) return len;
+            lenenc = ZIP_LEN_INLINE;
+            buf[0] = rawlen;
+        } else if (rawlen <= 0xffff) {
+            len += 2;
+            if (!p) return len;
+            lenenc = ZIP_LEN_UINT16;
+            buf[1] = (rawlen     ) & 0xff;
+            buf[2] = (rawlen >> 8) & 0xff;
         } else {
-            p[0] = ZIP_BIGLEN;
-            memcpy(p+1,&len,sizeof(len));
-            return 1+sizeof(len);
+            len += 4;
+            if (!p) return len;
+            lenenc = ZIP_LEN_UINT32;
+            buf[1] = (rawlen      ) & 0xff;
+            buf[2] = (rawlen >>  8) & 0xff;
+            buf[3] = (rawlen >> 16) & 0xff;
+            buf[4] = (rawlen >> 24) & 0xff;
         }
+        buf[0] = (lenenc << 4) | (buf[0] & 0xf);
+    }
+    if (!p) return len;
+
+    /* Apparently we need to store the length in 'p' */
+    buf[0] = (encoding << 6) | (buf[0] & 0x3f);
+    memcpy(p,buf,len);
+    return len;
+}
+
+/* Check if string pointed to by 'entry' can be encoded as an integer.
+ * Stores the integer value in 'v' and its encoding in 'encoding'.
+ * Warning: this function requires a NULL-terminated string! */
+static int zipTryEncoding(unsigned char *entry, long long *v, char *encoding) {
+    long long value;
+    char *eptr;
+
+    if (entry[0] == '-' || (entry[0] >= '0' && entry[0] <= '9')) {
+        value = strtoll(entry,&eptr,10);
+        if (eptr[0] != '\0') return 0;
+        if (value >= SHRT_MIN && value <= SHRT_MAX) {
+            *encoding = ZIP_ENC_SHORT;
+        } else if (value >= INT_MIN && value <= INT_MAX) {
+            *encoding = ZIP_ENC_INT;
+        } else {
+            *encoding = ZIP_ENC_LLONG;
+        }
+        *v = value;
+        return 1;
+    }
+    return 0;
+}
+
+static void zipSaveInteger(unsigned char *p, long long value, char encoding) {
+    short int s;
+    int i;
+    long long l;
+    if (encoding == ZIP_ENC_SHORT) {
+        s = value;
+        memcpy(p,&s,sizeof(s));
+    } else if (encoding == ZIP_ENC_INT) {
+        i = value;
+        memcpy(p,&i,sizeof(i));
+    } else if (encoding == ZIP_ENC_LLONG) {
+        l = value;
+        memcpy(p,&l,sizeof(l));
+    } else {
+        assert(NULL);
+    }
+}
+
+static long long zipLoadInteger(unsigned char *p, char encoding) {
+    short int s;
+    int i;
+    long long l, ret;
+    if (encoding == ZIP_ENC_SHORT) {
+        memcpy(&s,p,sizeof(s));
+        ret = s;
+    } else if (encoding == ZIP_ENC_INT) {
+        memcpy(&i,p,sizeof(i));
+        ret = i;
+    } else if (encoding == ZIP_ENC_LLONG) {
+        memcpy(&l,p,sizeof(l));
+        ret = l;
+    } else {
+        assert(NULL);
     }
+    return ret;
 }
 
 /* Return the total amount used by an entry (encoded length + payload). */
 static unsigned int zipRawEntryLength(unsigned char *p) {
-    unsigned int l = zipDecodeLength(p);
-    return zipEncodeLength(NULL,l) + l;
+    unsigned int lensize, len;
+    len = zipDecodeLength(p, &lensize);
+    return lensize + len;
 }
 
 /* Resize the zip* structure. */

diff --git a/ziplist.c b/ziplist.c
index 596217d5fbf9e946ba60b9a8330740058bd2719b..a45ae339ad02d11be59581f729c52e0e3ec02524 100644 (file)
--- a/ziplist.c
+++ b/ziplist.c
@@ -15,8 +15,10 @@
  */
 
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 #include <assert.h>
+#include <limits.h>
 #include "zmalloc.h"
 #include "sds.h"
 #include "ziplist.h"
@@ -60,13 +62,21 @@ static unsigned char *ziplistTail(unsigned char *zl) {
 }
 
 unsigned char *ziplistPush(unsigned char *zl, unsigned char *entry, unsigned int elen, int where) {
-    unsigned int curlen = ZIPLIST_BYTES(zl);
-    unsigned int reqlen = zipEncodeLength(NULL,elen)+elen;
+    unsigned int curlen = ZIPLIST_BYTES(zl), reqlen;
     unsigned char *p;
+    char encoding = ZIP_ENC_RAW;
+    long long value;
 
-    /* Resize the ziplist */
-    zl = ziplistResize(zl,curlen+reqlen);
+    /* See if the entry can be encoded */
+    if (zipTryEncoding(entry,&value,&encoding)) {
+        reqlen = zipEncodingSize(encoding);
+    } else {
+        reqlen = elen;
+    }
+    reqlen += zipEncodeLength(NULL,encoding,elen);
 
+    /* Resize the ziplist and move if needed */
+    zl = ziplistResize(zl,curlen+reqlen);
     if (where == ZIPLIST_HEAD) {
         p = zl+ZIPLIST_HEADER_SIZE;
         if (*p != ZIP_END) {
@@ -78,31 +88,44 @@ unsigned char *ziplistPush(unsigned char *zl, unsigned char *entry, unsigned int
     }
 
     /* Write the entry */
-    p += zipEncodeLength(p,elen);
-    memcpy(p,entry,elen);
+    p += zipEncodeLength(p,encoding,elen);
+    if (encoding != ZIP_ENC_RAW) {
+        zipSaveInteger(p,value,encoding);
+    } else {
+        memcpy(p,entry,elen);
+    }
     ZIPLIST_INCR_LENGTH(zl,1);
     return zl;
 }
 
-unsigned char *ziplistPop(unsigned char *zl, sds *value, int where) {
-    unsigned int curlen = ZIPLIST_BYTES(zl), len, rlen;
+unsigned char *ziplistPop(unsigned char *zl, sds *target, int where) {
+    unsigned int curlen = ZIPLIST_BYTES(zl), rawlen;
+    unsigned int len, lensize;
     unsigned char *p;
-    if (value) *value = NULL;
+    long long value;
+    if (target) *target = NULL;
 
     /* Get pointer to element to remove */
     p = (where == ZIPLIST_HEAD) ? ziplistHead(zl) : ziplistTail(zl);
     if (*p == ZIP_END) return zl;
-    len = zipDecodeLength(p);
-    if (value) *value = sdsnewlen(p+zipEncodeLength(NULL,len),len);
+    len = zipDecodeLength(p,&lensize);
+    if (target) {
+        if (ZIP_ENCODING(p) == ZIP_ENC_RAW) {
+            *target = sdsnewlen(p+lensize,len);
+        } else {
+            value = zipLoadInteger(p+lensize,ZIP_ENCODING(p));
+            *target = sdscatprintf(sdsempty(), "%lld", value);
+        }
+    }
 
     /* Move list to front when popping from the head */
-    rlen = zipRawEntryLength(p);
+    rawlen = lensize+len;
     if (where == ZIPLIST_HEAD) {
-        memmove(p,p+rlen,curlen-ZIPLIST_HEADER_SIZE-len);
+        memmove(p,p+rawlen,curlen-ZIPLIST_HEADER_SIZE-len);
     }
 
     /* Resize and update length */
-    zl = ziplistResize(zl,curlen-rlen);
+    zl = ziplistResize(zl,curlen-rawlen);
     ZIPLIST_INCR_LENGTH(zl,-1);
     return zl;
 }
@@ -121,10 +144,11 @@ unsigned char *ziplistIndex(unsigned char *zl, unsigned int index) {
 /* Store entry at current position in sds *value and return pointer
  * to the next entry. */
 unsigned char *ziplistNext(unsigned char *p, unsigned char **q, unsigned char **entry, unsigned int *elen) {
+    unsigned int lensize;
     if (*p == ZIP_END) return NULL;
     if (entry) {
-        *elen = zipDecodeLength(p);
-        *entry = p+ZIP_LEN_BYTES(*elen);
+        *elen = zipDecodeLength(p,&lensize);
+        *entry = p+lensize;
     }
     if (q != NULL) *q = p;
     p += zipRawEntryLength(p);
@@ -174,16 +198,22 @@ unsigned char *ziplistDelete(unsigned char *zl, unsigned char **p) {
 }
 
 void ziplistRepr(unsigned char *zl) {
-    unsigned char *p;
-    unsigned int l;
+    unsigned char *p, encoding;
+    unsigned int l, lsize;
+    long long value;
 
-    printf("{bytes %d} {length %u}\n",ZIPLIST_BYTES(zl), ZIPLIST_LENGTH(zl));
+    printf("{total bytes %d} {length %u}\n",ZIPLIST_BYTES(zl), ZIPLIST_LENGTH(zl));
     p = ziplistHead(zl);
     while(*p != ZIP_END) {
-        l = zipDecodeLength(p);
-        printf("{key %u}",l);
-        p += zipEncodeLength(NULL,l);
-        fwrite(p,l,1,stdout);
+        l = zipDecodeLength(p,&lsize);
+        printf("{header %u, payload %u} ",lsize,l);
+        encoding = ZIP_ENCODING(p);
+        p += lsize;
+        if (encoding == ZIP_ENC_RAW) {
+            fwrite(p,l,1,stdout);
+        } else {
+            printf("%lld", zipLoadInteger(p,encoding));
+        }
         printf("\n");
         p += l;
     }
@@ -200,11 +230,33 @@ unsigned char *createList() {
     return zl;
 }
 
+unsigned char *createIntList() {
+    unsigned char *zl = ziplistNew();
+    char buf[32];
+
+    sprintf(buf, "100");
+    zl = ziplistPush(zl, buf, strlen(buf), ZIPLIST_TAIL);
+    sprintf(buf, "128000");
+    zl = ziplistPush(zl, buf, strlen(buf), ZIPLIST_TAIL);
+    sprintf(buf, "-100");
+    zl = ziplistPush(zl, buf, strlen(buf), ZIPLIST_HEAD);
+    sprintf(buf, "4294967296");
+    zl = ziplistPush(zl, buf, strlen(buf), ZIPLIST_HEAD);
+    sprintf(buf, "non integer");
+    zl = ziplistPush(zl, buf, strlen(buf), ZIPLIST_TAIL);
+    sprintf(buf, "much much longer non integer");
+    zl = ziplistPush(zl, buf, strlen(buf), ZIPLIST_TAIL);
+    return zl;
+}
+
 int main(int argc, char **argv) {
     unsigned char *zl, *p, *q, *entry;
     unsigned int elen;
     sds s;
 
+    zl = createIntList();
+    ziplistRepr(zl);
+
     zl = createList();
     ziplistRepr(zl);