xo_encoder.c revision 300925 
1/*
2 * Copyright (c) 2015, Juniper Networks, Inc.
3 * All rights reserved.
4 * This SOFTWARE is licensed under the LICENSE provided in the
5 * ../Copyright file. By downloading, installing, copying, or otherwise
6 * using the SOFTWARE, you agree to be bound by the terms of that
7 * LICENSE.
8 * Phil Shafer, August 2015
9 */
10
11/**
12 * libxo includes a number of fixed encoding styles.  But other
13 * external encoders are need to deal with new encoders.  Rather
14 * than expose a swarm of libxo internals, we create a distinct
15 * API, with a simpler API than we use internally.
16 */
17
18#include <stdio.h>
19#include <unistd.h>
20#include <string.h>
21#include <sys/queue.h>
22#include <sys/param.h>
23#include <dlfcn.h>
24
25#include "xo_config.h"
26#include "xo.h"
27#include "xo_encoder.h"
28
29#ifdef HAVE_DLFCN_H
30#include <dlfcn.h>
31#if !defined(HAVE_DLFUNC)
32#define dlfunc(_p, _n)		dlsym(_p, _n)
33#endif
34#else /* HAVE_DLFCN_H */
35#define dlopen(_n, _f)		NULL /* Fail */
36#define dlsym(_p, _n)		NULL /* Fail */
37#define dlfunc(_p, _n)		NULL /* Fail */
38#endif /* HAVE_DLFCN_H */
39
40static void xo_encoder_setup (void); /* Forward decl */
41
42/*
43 * Need a simple string collection
44 */
45typedef struct xo_string_node_s {
46    TAILQ_ENTRY(xo_string_node_s) xs_link; /* Next string */
47    char xs_data[0];		      /* String data */
48} xo_string_node_t;
49
50typedef TAILQ_HEAD(xo_string_list_s, xo_string_node_s) xo_string_list_t;
51
52static inline void
53xo_string_list_init (xo_string_list_t *listp)
54{
55    if (listp->tqh_last == NULL)
56	TAILQ_INIT(listp);
57}
58
59static inline xo_string_node_t *
60xo_string_add (xo_string_list_t *listp, const char *str)
61{
62    if (listp == NULL || str == NULL)
63	return NULL;
64
65    xo_string_list_init(listp);
66    size_t len = strlen(str);
67    xo_string_node_t *xsp;
68
69    xsp = xo_realloc(NULL, sizeof(*xsp) + len + 1);
70    if (xsp) {
71	memcpy(xsp->xs_data, str, len);
72	xsp->xs_data[len] = '\0';
73	TAILQ_INSERT_TAIL(listp, xsp, xs_link);
74    }
75
76    return xsp;
77}
78
79#define XO_STRING_LIST_FOREACH(_xsp, _listp) \
80    xo_string_list_init(_listp); \
81    TAILQ_FOREACH(_xsp, _listp, xs_link)
82
83static inline void
84xo_string_list_clean (xo_string_list_t *listp)
85{
86    xo_string_node_t *xsp;
87
88    xo_string_list_init(listp);
89
90    for (;;) {
91	xsp = TAILQ_FIRST(listp);
92        if (xsp == NULL)
93            break;
94        TAILQ_REMOVE(listp, xsp, xs_link);
95	xo_free(xsp);
96    }
97}
98
99static xo_string_list_t xo_encoder_path;
100
101void
102xo_encoder_path_add (const char *path)
103{
104    xo_encoder_setup();
105
106    if (path)
107	xo_string_add(&xo_encoder_path, path);
108}
109
110/* ---------------------------------------------------------------------- */
111
112typedef struct xo_encoder_node_s {
113    TAILQ_ENTRY(xo_encoder_node_s) xe_link; /* Next session */
114    char *xe_name;			/* Name for this encoder */
115    xo_encoder_func_t xe_handler;	/* Callback function */
116    void *xe_dlhandle;			/* dlopen handle */
117} xo_encoder_node_t;
118
119typedef TAILQ_HEAD(xo_encoder_list_s, xo_encoder_node_s) xo_encoder_list_t;
120
121#define XO_ENCODER_LIST_FOREACH(_xep, _listp) \
122    xo_encoder_list_init(_listp); \
123    TAILQ_FOREACH(_xep, _listp, xe_link)
124
125static xo_encoder_list_t xo_encoders;
126
127static void
128xo_encoder_list_init (xo_encoder_list_t *listp)
129{
130    if (listp->tqh_last == NULL)
131	TAILQ_INIT(listp);
132}
133
134static xo_encoder_node_t *
135xo_encoder_list_add (const char *name)
136{
137    if (name == NULL)
138	return NULL;
139
140    xo_encoder_node_t *xep = xo_realloc(NULL, sizeof(*xep));
141    if (xep) {
142	int len = strlen(name) + 1;
143	xep->xe_name = xo_realloc(NULL, len);
144	if (xep->xe_name == NULL) {
145	    xo_free(xep);
146	    return NULL;
147	}
148
149	memcpy(xep->xe_name, name, len);
150
151	TAILQ_INSERT_TAIL(&xo_encoders, xep, xe_link);
152    }
153
154    return xep;
155}
156
157void
158xo_encoders_clean (void)
159{
160    xo_encoder_node_t *xep;
161
162    xo_encoder_setup();
163
164    for (;;) {
165	xep = TAILQ_FIRST(&xo_encoders);
166        if (xep == NULL)
167            break;
168
169        TAILQ_REMOVE(&xo_encoders, xep, xe_link);
170
171	if (xep->xe_dlhandle)
172	    dlclose(xep->xe_dlhandle);
173
174	xo_free(xep);
175    }
176
177    xo_string_list_clean(&xo_encoder_path);
178}
179
180static void
181xo_encoder_setup (void)
182{
183    static int initted;
184    if (!initted) {
185	initted = 1;
186
187	xo_string_list_init(&xo_encoder_path);
188	xo_encoder_list_init(&xo_encoders);
189
190	xo_encoder_path_add(XO_ENCODERDIR);
191    }
192}
193
194static xo_encoder_node_t *
195xo_encoder_find (const char *name)
196{
197    xo_encoder_node_t *xep;
198
199    xo_encoder_list_init(&xo_encoders);
200
201    XO_ENCODER_LIST_FOREACH(xep, &xo_encoders) {
202	if (strcmp(xep->xe_name, name) == 0)
203	    return xep;
204    }
205
206    return NULL;
207}
208
209static xo_encoder_node_t *
210xo_encoder_discover (const char *name)
211{
212    void *dlp = NULL;
213    char buf[MAXPATHLEN];
214    xo_string_node_t *xsp;
215    xo_encoder_node_t *xep = NULL;
216
217    XO_STRING_LIST_FOREACH(xsp, &xo_encoder_path) {
218	static const char fmt[] = "%s/%s.enc";
219	char *dir = xsp->xs_data;
220	size_t len = snprintf(buf, sizeof(buf), fmt, dir, name);
221
222	if (len > sizeof(buf))	/* Should not occur */
223	    continue;
224
225	dlp = dlopen((const char *) buf, RTLD_NOW);
226	if (dlp)
227	    break;
228    }
229
230    if (dlp) {
231	/*
232	 * If the library exists, find the initializer function and
233	 * call it.
234	 */
235	xo_encoder_init_func_t func;
236
237	func = (xo_encoder_init_func_t) dlfunc(dlp, XO_ENCODER_INIT_NAME);
238	if (func) {
239	    xo_encoder_init_args_t xei;
240
241	    bzero(&xei, sizeof(xei));
242
243	    xei.xei_version = XO_ENCODER_VERSION;
244	    int rc = func(&xei);
245	    if (rc == 0 && xei.xei_handler) {
246		xep = xo_encoder_list_add(name);
247		if (xep) {
248		    xep->xe_handler = xei.xei_handler;
249		    xep->xe_dlhandle = dlp;
250		}
251	    }
252	}
253
254	if (xep == NULL)
255	    dlclose(dlp);
256    }
257
258    return xep;
259}
260
261void
262xo_encoder_register (const char *name, xo_encoder_func_t func)
263{
264    xo_encoder_setup();
265
266    xo_encoder_node_t *xep = xo_encoder_find(name);
267
268    if (xep)			/* "We alla-ready got one" */
269	return;
270
271    xep = xo_encoder_list_add(name);
272    if (xep)
273	xep->xe_handler = func;
274}
275
276void
277xo_encoder_unregister (const char *name)
278{
279    xo_encoder_setup();
280
281    xo_encoder_node_t *xep = xo_encoder_find(name);
282    if (xep) {
283	TAILQ_REMOVE(&xo_encoders, xep, xe_link);
284	xo_free(xep);
285    }
286}
287
288int
289xo_encoder_init (xo_handle_t *xop, const char *name)
290{
291    xo_encoder_setup();
292
293    /* Can't have names containing '/' or ':' */
294    if (strchr(name, '/') != NULL || strchr(name, ':') != NULL)
295	return -1;
296
297   /*
298     * First we look on the list of known (registered) encoders.
299     * If we don't find it, we follow the set of paths to find
300     * the encoding library.
301     */
302    xo_encoder_node_t *xep = xo_encoder_find(name);
303    if (xep == NULL) {
304	xep = xo_encoder_discover(name);
305	if (xep == NULL)
306	    return -1;
307    }
308
309    xo_set_encoder(xop, xep->xe_handler);
310
311    return xo_encoder_handle(xop, XO_OP_CREATE, NULL, NULL);
312}
313
314/*
315 * A couple of function varieties here, to allow for multiple
316 * use cases.  This variant is for when the main program knows
317 * its own encoder needs.
318 */
319xo_handle_t *
320xo_encoder_create (const char *name, xo_xof_flags_t flags)
321{
322    xo_handle_t *xop;
323
324    xop = xo_create(XO_STYLE_ENCODER, flags);
325    if (xop) {
326	if (xo_encoder_init(xop, name)) {
327	    xo_destroy(xop);
328	    xop = NULL;
329	}
330    }
331
332    return xop;
333}
334
335int
336xo_encoder_handle (xo_handle_t *xop, xo_encoder_op_t op,
337		  const char *name, const char *value)
338{
339    void *private = xo_get_private(xop);
340    xo_encoder_func_t func = xo_get_encoder(xop);
341
342    if (func == NULL)
343	return -1;
344
345    return func(xop, op, name, value, private);
346}
347
348const char *
349xo_encoder_op_name (xo_encoder_op_t op)
350{
351    static const char *names[] = {
352	/*  0 */ "unknown",
353	/*  1 */ "create",
354	/*  2 */ "open_container",
355	/*  3 */ "close_container",
356	/*  4 */ "open_list",
357	/*  5 */ "close_list",
358	/*  6 */ "open_leaf_list",
359	/*  7 */ "close_leaf_list",
360	/*  8 */ "open_instance",
361	/*  9 */ "close_instance",
362	/* 10 */ "string",
363	/* 11 */ "content",
364	/* 12 */ "finish",
365	/* 13 */ "flush",
366	/* 14 */ "destroy",
367	/* 15 */ "attr",
368	/* 16 */ "version",
369    };
370
371    if (op > sizeof(names) / sizeof(names[0]))
372	return "unknown";
373
374    return names[op];
375}
376