sbase

suckless unix tools
git clone git://git.2f30.org/sbase.git
Log | Files | Refs | README | LICENSE

commit b44d4d8edd2d57d2b757436e4a958b8c648c0b63
parent fad1d353575bf03f4bf5a9e6c14eb7607b139d6c
Author: Mattias Andrée <maandree@kth.se>
Date:   Wed Feb 17 01:17:33 +0100

Add tsort(1)

Signed-off-by: Mattias Andrée <maandree@kth.se>

Diffstat:
Makefile | 1+
README | 1+
tsort.1 | 72++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
tsort.c | 218+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 292 insertions(+), 0 deletions(-)
diff --git a/Makefile b/Makefile @@ -150,6 +150,7 @@ BIN =\ touch\ tr\ true\ + tsort\ tty\ uname\ unexpand\ diff --git a/README b/README @@ -89,6 +89,7 @@ The following tools are implemented: =*|o touch . #*|o tr . =*|o true . +=* o tsort . =*|o tty . =*|o uname . #*|o unexpand . diff --git a/tsort.1 b/tsort.1 @@ -0,0 +1,72 @@ +.Dd 2016-02-16 +.Dt TSORT 1 +.Os sbase +.Sh NAME +.Nm tsort +.Nd topological sort +.Sh SYNOPSIS +.Nm +.Op Ar file +.Sh DESCRIPTION +.Nm +topologically sorts a graph. The graph is read +either from +.Ar file +or from standard input. The result is not optimized +for any particular usage. Loops are detected and +reported to standard error, but does not stop the sort. +.Pp +The input is a list of edges (vertex pairs), where +the edge is directed from the first vertex to the +second vertex. +.Sh OPTIONS +None. +.Sh EXIT STATUS +.Bl -tag -width Ds +.It 0 +The graph as successfully sorted. +.It 1 +The graph as successfully sorted, but contained loops. +.It > 1 +An error occurred. +.El +.Sh EXAMPLES +The input + + a a + a b + a c + a c + a d + b c + c b + e f + +or equivalently + + a a a b a c a c a d + b c c b e f + +represents the graph + + ┌─┐ + ↓ │ + ┏━━━┓ + ┌──────┃ a ┃──────┐ + │ ┗━━━┛ │ + │ │ │ │ + ↓ ↓ ↓ ↓ + ┏━━━┓───→┏━━━┓ ┏━━━┓ + ┃ b ┃ ┃ c ┃ ┃ d ┃ + ┗━━━┛←───┗━━━┛ ┗━━━┛ + + ┏━━━┓ ┏━━━┓ + ┃ e ┃───→┃ f ┃ + ┗━━━┛ ┗━━━┛ + +.Sh STANDARDS +The +.Nm +utility is compliant with the +.St -p1003.1-2013 +specification. diff --git a/tsort.c b/tsort.c @@ -0,0 +1,218 @@ +/* See LICENSE file for copyright and license details. */ +#include <stdio.h> +#include <string.h> +#include <stdlib.h> +#include <ctype.h> + +#include "util.h" + +#define eprintf(...) enprintf(2, __VA_ARGS__) +#define estrdup(...) enstrdup(2, __VA_ARGS__) +#define ecalloc(...) encalloc(2, __VA_ARGS__) +#define efshut(...) enfshut(2, __VA_ARGS__) + +#define WHITE 0 +#define GREY 1 +#define BLACK 2 + +struct vertex; + +struct edge +{ + struct vertex *to; + struct edge *next; +}; + +struct vertex +{ + char *name; + struct vertex *next; + struct edge edges; + size_t in_edges; + int colour; +}; + +static struct vertex graph; + +static void +find_vertex(const char *name, struct vertex **it, struct vertex **prev) +{ + for (*prev = &graph; (*it = (*prev)->next); *prev = *it) { + int cmp = strcmp(name, (*it)->name); + if (cmp > 0) + continue; + if (cmp < 0) + *it = 0; + return; + } +} + +static void +find_edge(struct vertex* from, const char *to, struct edge **it, struct edge **prev) +{ + for (*prev = &(from->edges); (*it = (*prev)->next); *prev = *it) { + int cmp = strcmp(to, (*it)->to->name); + if (cmp > 0) + continue; + if (cmp < 0) + *it = 0; + return; + } +} + +static struct vertex * +add_vertex(char *name) +{ + struct vertex *vertex; + struct vertex *prev; + + find_vertex(name, &vertex, &prev); + if (vertex) + return vertex; + + vertex = ecalloc(1, sizeof(*vertex)); + vertex->name = name; + vertex->next = prev->next; + prev->next = vertex; + + return vertex; +} + +static struct edge * +add_edge(struct vertex* from, struct vertex* to) +{ + struct edge *edge; + struct edge *prev; + + find_edge(from, to->name, &edge, &prev); + if (edge) + return edge; + + edge = ecalloc(1, sizeof(*edge)); + edge->to = to; + edge->next = prev->next; + prev->next = edge; + to->in_edges += 1; + + return edge; +} + +static void +load_graph(FILE *fp) +{ +#define SKIP(VAR, START, FUNC) for (VAR = START; FUNC(*VAR) && *VAR; VAR++) +#define TOKEN_END(P) do { if (*P) *P++ = 0; else P = 0; } while (0) + + char *line = 0; + size_t size = 0; + ssize_t len; + char *p; + char *name; + struct vertex *from = 0; + + while ((len = getline(&line, &size, fp)) != -1) { + if (len && line[len - 1] == '\n') + line[len - 1] = 0; + for (p = line; p;) { + SKIP(name, p, isspace); + if (!*name) + break; + SKIP(p, name, !isspace); + TOKEN_END(p); + if (!from) { + from = add_vertex(estrdup(name)); + } else if (strcmp(from->name, name)) { + add_edge(from, add_vertex(estrdup(name))); + from = 0; + } else { + from = 0; + } + } + } + + free(line); + + if (from) + eprintf("odd number of tokens in input, did you intended to use -l?\n"); +} + +static int +sort_graph_visit(struct vertex *u) +{ + struct edge *e = &(u->edges); + struct vertex *v; + int r = 0; + u->colour = GREY; + printf("%s\n", u->name); + while ((e = e->next)) { + v = e->to; + if (v->colour == WHITE) { + v->in_edges -= 1; + if (v->in_edges == 0) + r |= sort_graph_visit(v); + } else if (v->colour == GREY) { + r = 1; + fprintf(stderr, "%s: loop detected between %s and %s\n", + argv0, u->name, v->name); + } + } + u->colour = BLACK; + return r; +} + +static int +sort_graph(void) +{ + struct vertex *u, *prev; + int r = 0; + size_t in_edges; + for (in_edges = 0; graph.next; in_edges++) { + for (prev = &graph; (u = prev->next); prev = u) { + if (u->colour != WHITE) + goto unlist; + if (u->in_edges > in_edges) + continue; + r |= sort_graph_visit(u); + unlist: + prev->next = u->next; + u = prev; + } + } + return r; +} + +static void +usage(void) +{ + eprintf("usage: %s [file]\n", argv0); +} + +int +main(int argc, char *argv[]) +{ + FILE *fp = stdin; + const char *fn = "<stdin>"; + int ret = 0; + + ARGBEGIN { + default: + usage(); + } ARGEND; + + if (argc > 1) + usage(); + if (argc && strcmp(*argv, "-")) + if (!(fp = fopen(fn = *argv, "r"))) + eprintf("fopen %s:", *argv); + + memset(&graph, 0, sizeof(graph)); + load_graph(fp); + efshut(fp, fn); + + ret = sort_graph(); + + if (fshut(stdout, "<stdout>") | fshut(stderr, "<stderr>")) + ret = 2; + + return ret; +}