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# testing files
build
build.ninja
ngen.toml
tree.c
tree.pdf
tv.c

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# treeviz
A header-only C library which uses [graphviz](https://www.graphviz.org/) to
visualize recursive data structures.
This library is intended mostly for debugging purposes, as it can oftentimes
be useful to visualize your program's data layout. This is especially true with
deeply nested recursive data structures.
The methods in this library use two functions that end-user must write
themselves:
1. One that iterates over a node's children,
1. And another that represents a node's data.
This design allows the library to work with **any recursive data structure.**
As it turns out, these two functions are all you need to generalize the task
of visualization.
## Dependencies
You must have graphviz installed, and the `dot` executable in your path. That's
it.
*Optional:* Becuase this library renders your tree to a pdf (for now), it is
nice to have a pdf viewer that updates the screen automatically upon an update
to the file being viewed. [Zathura](https://github.com/pwmt/zathura) is one such
viewer, but there are many available.
## TODO: write documentation
There are some notes in the header file that may guide you before I write the
actual docs.
---
Copyright (C) Noah Swerhun under the terms of the LGPLv3 (see LICENSE.txt).

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#ifndef TREEVIZ_H
#define TREEVIZ_H
// TreeViz context. Contains settings for the visualizer functions. This
// is wrapped in a struct so you don't have to always pass the same options
// to every funcion call. However, if you want to do that, you can use the
// `TV_vizl` function.
typedef struct TVCtx_T {
// Output filename. Should end in `.pdf`
char *filename;
// Function that takes a reference to a node, and returns a string
// representing the node's data. The representation should not include any
// information about children, just the data stored in the node that the
// function was called on.
char *(*represent_data)(void *node);
// A function that takes a node, and iteratively returns each child of the
// node on each successive call, setting `done` to 1 when all children have
// been processed. Be sure to use `cur_idx` to track the function's progress:
// this function will be called in a recursive context, so using static memory
// introduces some funny bugs.
void *(*next_child)(void *root_node, int *done, int *cur_idx);
} TVCtx;
// Visualize the tree rooted at `root_node`, using the settings found in `ctx`.
void TV_vizv(void *root_node, TVCtx *ctx);
// Visualize the tree rooted at `root_node`, using the settings specifed. See
// the `TVCtx` struct.
void TV_vizl(void *root_node, char *filename,
char *(*represent_data)(void *root_node),
void *(*next_child)(void *root_node, int *done, int *cur_idx));
#endif
#ifdef TREEVIZ_IMPLEMENTATION
#ifndef TREEVIZ_IMPL_ALREADY
#define TREEVIZ_IMPL_ALREADY
#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/wait.h>
#include <unistd.h>
#define ERRCHECK(...) \
if (errno != 0) { \
fprintf(stderr, "error: %s (errno %d)\n", strerror(errno), errno); \
fprintf(stderr, __VA_ARGS__); \
fputc('\n', stderr); \
assert(errno == 0); \
}
#define NOT_NULL(x) assert(x != NULL)
void _TV_write_dot(void *root_node, int fd, TVCtx *ctx, size_t *id) {
void *(*next_child)(void *root_node, int *done, int *cur_idx) =
ctx->next_child;
char *(*represent_data)(void *node) = ctx->represent_data;
char *repr = represent_data(root_node);
size_t cur_id = *id;
++(*id);
errno = 0;
if (root_node == NULL) {
dprintf(fd, "%zu [style=filled,fillcolor=gray,label=\"%s\"];", cur_id,
repr);
} else {
dprintf(fd, "%zu [label=\"%s\"];", cur_id, repr);
}
ERRCHECK("TreeViz: _TV_write_dot: could not write to pipe");
free(repr);
if (root_node == NULL) {
return;
}
int done = 0;
int iter = 0;
while (!done) {
void *child = next_child(root_node, &done, &iter);
errno = 0;
dprintf(fd, "%zu->%zu;", cur_id, *id);
ERRCHECK("TreeViz: _TV_write_dot: could not write to pipe");
_TV_write_dot(child, fd, ctx, id);
}
}
void TV_vizv(void *root_node, TVCtx *ctx) {
int pipe_stdin[2];
errno = 0;
pipe(pipe_stdin);
ERRCHECK("TreeViz: TV_vizv: could not create pipe to dot")
int child_stdin_write = pipe_stdin[1];
int child_stdin_read = pipe_stdin[0];
char o_argument[1024] = "-o";
strncat(o_argument, ctx->filename, 1021);
errno = 0;
pid_t pid = fork();
ERRCHECK("TreeViz: TV_vizv: could not fork process");
if (pid == 0) {
//// CHILD PROCESS
close(child_stdin_write);
ERRCHECK("TreeViz: TV_vizv: CHILD: could not close old pipe, write end");
dup2(child_stdin_read, STDIN_FILENO);
ERRCHECK("TreeViz: TV_vizv: CHILD: could not set stdin fileno");
close(child_stdin_read);
ERRCHECK("TreeViz: TV_vizv: CHILD: could not close old pipe, read end");
char *run = "dot";
execlp(run, run, "-Tpdf", o_argument);
ERRCHECK("TreeViz: TV_vizv: CHILD: could not exec `%s`.\n\nDo you have "
"graphviz installed and in your PATH?\n",
run);
} else {
//// PARENT PROCESS
close(child_stdin_read);
ERRCHECK("TreeViz: TV_vizv: could not close old pipe, read end");
dprintf(child_stdin_write, "digraph{node [shape=rect];");
ERRCHECK("TreeViz: TV_vizv: could not write to pipe");
size_t id = 0;
_TV_write_dot(root_node, child_stdin_write, ctx, &id);
errno = 0;
dprintf(child_stdin_write, "}");
ERRCHECK("TreeViz: TV_vizv: could not write to pipe");
close(child_stdin_write);
ERRCHECK("TreeViz: TV_vizv: could not close old pipe, write end");
int status;
wait(&status);
ERRCHECK("TreeViz: TV_vizv: could not wait on child process");
if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
fprintf(stderr, "TreeViz: TV_vizv: dot process failed. "
"terminating immediately.\n");
assert(status == 0);
}
}
}
void TV_vizl(void *root_node, char *filename,
char *(*represent_data)(void *root_node),
void *(*next_child)(void *root_node, int *done, int *cur_idx)) {
TVCtx ctx = {filename, represent_data, next_child};
TV_vizv(root_node, &ctx);
}
#endif
#endif