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@ -32,82 +32,83 @@ |
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
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.\" SUCH DAMAGE. |
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.\" SUCH DAMAGE. |
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.\" |
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.\" |
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.\" $OpenBSD: bm.3,v 1.3 1999/05/28 01:57:37 aaron Exp $ |
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.\" $OpenBSD: bm.3,v 1.4 1999/06/29 17:49:24 aaron Exp $ |
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.\" |
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.\" |
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.TH BM 3 |
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.SH NAME |
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bm_comp, bm_exec, bm_free \- Boyer-Moore string search |
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.SH SYNOPSIS |
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.ft B |
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#include <sys/types.h> |
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.br |
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#include <bm.h> |
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.sp |
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bm_pat * |
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.br |
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bm_comp(u_char *pattern, size_t patlen, u_char freq[256]); |
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.sp |
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u_char * |
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.br |
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bm_exec(bm_pat *pdesc, u_char *text, size_t len); |
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.sp |
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void |
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.br |
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bm_free(bm_pat *pdesc); |
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.SH DESCRIPTION |
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.Dd June 29, 1999 |
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.Dt BM 3 |
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.Os |
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.Sh NAME |
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.Nm bm_comp , |
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.Nm bm_exec , |
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.Nm bm_free |
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.Nd Boyer-Moore string search |
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.Sh SYNOPSIS |
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.Fd #include <sys/types.h> |
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.Fd #include <bm.h> |
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.Ft bm_pat * |
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.Fn bm_comp "u_char *pattern" "size_t patlen" "u_char freq[256]" |
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.Ft u_char * |
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.Fn bm_exec "bm_pat *pdesc" "u_char *text" "size_t len" |
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.Ft void |
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.Fn bm_free "bm_pat *pdesc" |
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.Sh DESCRIPTION |
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These routines implement an efficient mechanism to find an |
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These routines implement an efficient mechanism to find an |
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occurrence of a byte string within another byte string. |
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occurrence of a byte string within another byte string. |
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.PP |
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.I Bm_comp |
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evaluates the |
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.I patlen |
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.Pp |
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.Fn bm_comp |
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evaluates |
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.Fa patlen |
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bytes starting at |
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bytes starting at |
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.IR pattern , |
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.Fa pattern , |
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and returns a pointer to a structure describing them. |
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and returns a pointer to a structure describing them. |
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The bytes referenced by |
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The bytes referenced by |
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.I pattern |
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.Fa pattern |
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may be of any value. |
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may be of any value. |
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.PP |
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.Pp |
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The search takes advantage of the frequency distribution of the |
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The search takes advantage of the frequency distribution of the |
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bytes in the text to be searched. |
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bytes in the text to be searched. |
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If specified, |
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If specified, |
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.I freq |
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.Ar freq |
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should be an array of 256 values, |
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should be an array of 256 values, |
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with higher values indicating that the corresponding character occurs |
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with higher values indicating that the corresponding character occurs |
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more frequently. |
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more frequently. |
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(A less than optimal frequency distribution can only result in less |
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(A less than optimal frequency distribution can only result in less |
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than optimal performance, not incorrect results.) |
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than optimal performance, not incorrect results.) |
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If |
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If |
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.I freq |
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is NULL, |
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.Ar freq |
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is |
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.Dv NULL , |
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a system default table is used. |
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a system default table is used. |
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.PP |
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.I Bm_exec |
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.Pp |
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.Fn bm_exec |
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returns a pointer to the leftmost occurrence of the string given to |
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returns a pointer to the leftmost occurrence of the string given to |
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.I bm_comp |
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.Fn bm_comp |
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within |
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within |
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.IR text , |
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or NULL if none occurs. |
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.Ar text , |
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or |
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.Dv NULL |
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if none occurs. |
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The number of bytes in |
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The number of bytes in |
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.I text |
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.Ar text |
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must be specified by |
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must be specified by |
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.IR len . |
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.PP |
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.Ar len . |
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.Pp |
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Space allocated for the returned description is discarded |
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Space allocated for the returned description is discarded |
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by calling |
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by calling |
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.I bm_free |
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.Fn bm_free |
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with the returned description as an argument. |
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with the returned description as an argument. |
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.PP |
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.Pp |
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The asymptotic speed of |
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The asymptotic speed of |
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.I bm_exec |
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.Fn bm_exec |
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is |
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is |
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.RI O( len / patlen ). |
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.PP |
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.SH SEE ALSO |
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.IR regexp (3), |
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.IR strstr (3) |
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.sp |
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.IR "Fast String Searching" , |
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Hume and Sunday, |
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Software Practice and Experience, |
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Vol. 21, 11 (November 1991) pp. 1221-48. |
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.Pf O Ns Pq len / patlen . |
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.Sh SEE ALSO |
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.Xr regexp 3 , |
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.Xr strstr 3 |
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.Rs |
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.%R "Fast String Searching" |
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.%A "Hume and Sunday" |
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.%J "Software Practice and Experience" |
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.%V Volume 21, 11 (November 1991) |
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.%P 1221-48 |
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.Re |