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ICU-266 improve hashXXString() performance, add hashIString()

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X-SVN-Rev: 731
This commit is contained in:
Markus Scherer 2000-02-08 23:35:19 +00:00
parent 9c8cf9e12d
commit 139685dd3f
2 changed files with 77 additions and 16 deletions
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83
icu4c/source/common/uhash.c
View file

@ -505,7 +505,6 @@ uhash_hashUString(const void *parm)
int32_t len = u_strlen(key);
int32_t hash = UHASH_INVALID;
const UChar *limit = key + len;
int32_t inc = (len >= 128 ? len/64 : 1);
/*
We compute the hash by iterating sparsely over 64 (at most) characters
@ -515,17 +514,25 @@ uhash_hashUString(const void *parm)
thus producing a pseudorandom deterministic value which should be well
distributed over the output range. [LIU]
*/
while(key < limit) {
hash = (hash * 37) + *key;
key += inc;
if(len<=64) {
while(key < limit) {
hash = (hash * 37) + *key++;
}
} else {
int32_t inc = (len+63)/64;
while(key < limit) {
hash = (hash * 37) + *key;
key += inc;
}
}
hash &= 0x7FFFFFFF;
if(hash == UHASH_INVALID) {
hash = UHASH_EMPTY;
}
return hash & 0x7FFFFFFF;
return hash;
} else {
return UHASH_INVALID;
}
@ -539,7 +546,6 @@ uhash_hashString(const void *parm)
int32_t len = uprv_strlen(key);
int32_t hash = UHASH_INVALID;
const char *limit = key + len;
int32_t inc = (len >= 128 ? len/64 : 1);
/*
We compute the hash by iterating sparsely over 64 (at most) characters
@ -549,17 +555,59 @@ uhash_hashString(const void *parm)
thus producing a pseudorandom deterministic value which should be well
distributed over the output range. [LIU]
*/
while(key < limit) {
hash = (hash * 37) + *key;
key += inc;
if(len<=64) {
while(key < limit) {
hash = (hash * 37) + *key++;
}
} else {
int32_t inc = (len+63)/64;
while(key < limit) {
hash = (hash * 37) + *key;
key += inc;
}
}
hash &= 0x7FFFFFFF;
if(hash == UHASH_INVALID) {
hash = UHASH_EMPTY;
}
return hash & 0x7FFFFFFF;
return hash;
} else {
return UHASH_INVALID;
}
}
U_CAPI int32_t
uhash_hashIString(const void *parm)
{
if(parm != NULL) {
const char *key = (const char*) parm;
int32_t len = uprv_strlen(key);
int32_t hash = UHASH_INVALID;
const char *limit = key + len;
/* same as uhash_hashString(), but uses uprv_tolower(characters) */
if(len<=64) {
while(key < limit) {
hash = (hash * 37) + uprv_tolower(*key++);
}
} else {
int32_t inc = (len+63)/64;
while(key < limit) {
hash = (hash * 37) + uprv_tolower(*key);
key += inc;
}
}
hash &= 0x7FFFFFFF;
if(hash == UHASH_INVALID) {
hash = UHASH_EMPTY;
}
return hash;
} else {
return UHASH_INVALID;
}
@ -568,6 +616,9 @@ uhash_hashString(const void *parm)
U_CAPI int32_t
uhash_hashLong(const void *parm)
{
int32_t hash = (int32_t) parm;
return (int32_t) (hash & 0x7FFFFFFF);
int32_t hash = (int32_t) parm & 0x7FFFFFFF;
if(hash == UHASH_INVALID) {
hash = UHASH_EMPTY;
}
return hash;
}

10
icu4c/source/common/uhash.h
View file

@ -200,6 +200,16 @@ uhash_hashUString(const void *parm);
U_CAPI int32_t
uhash_hashString(const void *parm);
/**
* Generate a hash code for a null-terminated string in a case-insensitive way.
* If the string is not null-terminated the behavior of this
* function is undefined.
* @param parm The string (const char*) to hash.
* @return A hash code for parm.
*/
U_CAPI int32_t
uhash_hashIString(const void *parm);
/**
* Generate a hash code for long integer.
* @param parm The long (cast to void*) to hash.