nbperf(1) [netbsd man page]
NBPERF(1) BSD General Commands Manual NBPERF(1) NAME
nbperf -- compute a perfect hash function SYNOPSIS
nbperf [-ps] [-a algorithm] [-c utilisation] [-h hash] [-i iterations] [-m map-file] [-n name] [-o output] [input] DESCRIPTION
nbperf reads a number of keys one per line from standard input or input. It computes a minimal perfect hash function and writes it to stdout or output. The default algorithm is "chm". The -m argument instructs nbperf to write the resulting key mapping to map-file. Each line gives the result of the hash function for the corresponding input key. The parameter utilisation determines the space efficiency. Supported arguments for -a: chm This results in an order preserving minimal perfect hash function. The utilisation must be at least 2, the default. The number of iterations needed grows if the utilisation is very near to 2. chm3 Similar to chm. The resulting hash function needs three instead of two table lookups when compared to chm. The utilisation must be at least 1.24, the default. This makes the output for chm3 noticable smaller than the output for chm. bpz This results in a non-order preserving minimal perfect hash function. Output size is approximately 2.79 bit per key for the default value of utilisation, 1.24. This is also the smallest supported value. Supported arguments for -h: mi_vector_hash Platform-independent version of Jenkins parallel hash. See mi_vector_hash(3). The number of iterations can be limited with -i. nbperf outputs a function matching uint32_t hash(const void * restrict, size_t) to stdout. The function expects the key length as second argument, for strings not including the terminating NUL. It is the responsibility of the call- er to pass in only valid keys or compare the resulting index to the key. The function name can be changed using -n name. If the -s flag is specified, it will be static. After each failing iteration, a dot is written to stderr. nbperf checks for duplicate keys on the first iteration that passed basic hash distribution tests. In that case, an error message is printed and the program terminates. If the -p flag is specified, the hash function is seeded in a stable way. This may take longer than the normal random seed, but ensures that the output is the same for repeated invocations as long as the input is constant. EXIT STATUS
The nbperf utility exits 0 on success, and >0 if an error occurs. SEE ALSO
mi_vector_hash(3) AUTHORS
Jorg Sonnenberger BSD
September 25, 2012 BSD
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HASHSTASH(3) libbash hashstash Library Manual HASHSTASH(3) NAME
hashstash -- libbash library that implements hash data structure SYNOPSIS
hashSet <Value> <Key> <HashName> [SubHashName [...]] $retval hashGet <Key> <HashName> [SubHashName [...]] $retval hashKeys <HashName> [SubHashName [...]] hashRemove <Key> <HashName> [SubHashName [...]] hashDelete <HashName> [SubHashName [...]] DESCRIPTION
General hashstash is a collection of functions that implement basic hash data-structure in bash scripting language. The function list: hashSet Adds a value to the hash hashGet Returns a value from the hash hashKeys Returns a list of keys of the hash hashRemove Removes a key from the hash hashDelete Deletes a hash Detailed interface description follows. FUNCTIONS DESCRIPTIONS
hashSet <Value> <Key> <Hashname> [SubHashName [...]] Adds a value to the hash. Parameters: <Value> The value to set in HashName[Key]. <Key> The key for the value Value. <HashName> [SubHashName [...]] A string that contains the name of the hash. If the hash is a sub hash of another hash, the "father hash" name MUST BE WRITTEN FIRST, followed by the sub-hash name. Value will be the value of the key Key in the hash HashName. For example if you have (or want to define) hash C, which is subhash of hash B, which is subhash of hash A, and C has a key named ckey1 with value cval1, then you should use: hashSet cval1 ckey1 A B C $retval hashGet <Key> <HashName> [SubHashName [...]] Returns the value of Key in HashName to the $retval variable. Parameters: <Key> The key that hold the value we wish to get. <HashName> [SubHashName [...]] A string that contains the name of the hash. If the hash is a sub hash of another hash, the "father hash" name MUST BE WRITTEN FIRST, followed by the sub-hash name. Return Value: The value of the key Key in the hash HashName. The value is returned in the variable $retval. $retval hashKeys <HashName> [SubHashName [...]] Returns a list of keys of the hash HashName in the variable $retval. Parameters: <HashName> [SubHashName [...]] A string that contains the name of the hash. If the hash is a sub hash of another hash, the "father hash" name MUST BE WRITTEN FIRST, followed by the sub-hash name. Return Value: The value of the key Key in the hash HashName. The value is returned in the variable $retval. hashRemove <Key> <HashName> [SubHashName [...]] Removes the key Key from the hash HashName. <Key> The key we wish to remove from HashName. <HashName> [SubHashName [...]] A string that contains the name of the hash. If the hash is a sub hash of another hash, the "father hash" name MUST BE WRITTEN FIRST, followed by the sub-hash name. This function should also be used to remove a sub-hash from its "father hash". In that case, the key will be the name of the sub-hash. hashDelete <HashName> [SubHashName [...]] Deletes the hash HashName [SubHashName [...]]. Parameters: <HashName> [SubHashName [...]] A string that contains the name of the hash. If the hash is a sub hash of another hash, the "father hash" name MUST BE WRITTEN FIRST, followed by the sub-hash name. If this function is used on a sub-hash, a key with the name of the sub-hash will remain in its "father hash" and will hold a NULL value. BUGS
A hash name can only contain characters that are valid as part of bash variable names (i.e. a-zA-Z0-9_). The same applies for hash keys. As for now, there is no way of knowing if a key represents a value or a sub-hash. If a sub-hash will be used as a key, the returned value will be its keys list. EXAMPLES
Define hash table hashA with key Akey1 with value Aval1 use: % hashSet Aval1 Akey1 Ahash Now: % hashGet Akey1 Ahash % echo $retval Aval1 % hashKeys Ahash % echo $retval Akey1 % HISTORY
The idea to write hashstash library appeared when we've discovered the full power of the bash eval function. As of the name hashstash, it has two meanings. The first, it means 'stash' of hash functions. The second is, that hashstash contains sub- hashes inside, so it looks like stash of packed information. AUTHORS
Hai Zaar <haizaar@haizaar.com> Gil Ran <gil@ran4.net> SEE ALSO
ldbash(1), libbash(1) Linux Epoch Linux