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HUFF(3) Library Functions Manual HUFF(3) NAME huff - huffman codebook/tree generator SYNOPSIS #include <huff.h> NODE *huff(inrout) int (*inrout)(); DESCRIPTION Huff generates a binary Huffman codebook. It obtains a list of mes- sages one at a time from an input routine, inrout, declared as int inrout(str, p) char ** str; float *p; Inrout makes *str point to a null-terminated string identifying a mes- sage, and places in *p the (arbitrarily normalized) frequency of the message. Inrout returns non-zero when data is returned and zero when there is no more data. Huff returns a pointer to a root of type NODE: typedef struct node { char *datump; struct node *to; struct node *from; struct node *ldad; struct node *rdad; struct node *kid; float prob; } NODE; The root heads a linked list and the Huffman tree. The doubly linked list, connected via from and to, is ordered as the codebook was gener- ated. The tree is connected via kid, ldad, and rdad, with null point- ers at the various ends. The kid field points towards the root, ldad and rdad point away: node->ldad->kid==node and node->rdad->kid==node. the datump field is null or points to a message identifier. The codeword for a message may be read off from the path from the root to the node containing the message identifier, counting ldad branches as 0 and rdad branches as 1. BUGS A code with only one message dumps core. HUFF(3)