Root/fakefile/comm.c

1/*
2 * comm.c - Fakefile IPC functions
3 *
4 * Copyright 2012 by Werner Almesberger
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
10 */
11
12#include <stdint.h>
13#include <stdlib.h>
14#include <stdio.h>
15#include <unistd.h>
16#include <string.h>
17#include <assert.h>
18#include <sys/types.h>
19
20#include "util.h"
21#include "comm.h"
22
23
24#define BUF_SIZE 4096
25
26
27struct fakefile_peer {
28    int in, out;
29    uint8_t buf[BUF_SIZE];
30    void *pos;
31    const void *end;
32};
33
34
35struct fakefile_msg {
36    struct fakefile_peer *peer;
37    void *buf; /* NULL if reading */
38    void *pos; /* current position in buffer; write only */
39    size_t len; /* amount of data read/written so far */
40    size_t msg_size; /* declared size */
41    size_t buf_size; /* allocated size; write only */
42};
43
44
45static int master_fd(const char *name)
46{
47    const char *s;
48    char *end;
49    long n;
50
51    s = getenv(name);
52    if (!s) {
53        fprintf(stderr, "%s not set\n", name);
54        exit(1);
55    }
56    n = strtol(s, &end, 0);
57    if (*end || n < 0) {
58        fprintf(stderr, "invalid fd \"%s\" for %s\n", s, name);
59        exit(1);
60    }
61    return n;
62}
63
64
65static struct fakefile_peer *sanitize_peer(struct fakefile_peer *peer)
66{
67    static int have_peer = 0;
68    static struct fakefile_peer master;
69
70    if (peer)
71        return peer;
72    if (!have_peer) {
73        master.in = master_fd(FAKEFILE_MASTER_OUT_VAR);
74        master.out = master_fd(FAKEFILE_MASTER_IN_VAR);
75        master.pos = master.buf;
76        master.end = master.buf;
77        have_peer = 1;
78    }
79    return &master;
80}
81
82
83struct fakefile_peer *fakefile_peer(int in, int out)
84{
85    struct fakefile_peer *peer;
86
87    peer = alloc_type(struct fakefile_peer);
88    peer->in = in;
89    peer->out = out;
90    peer->pos = peer->buf;
91    peer->end = peer->buf;
92    return peer;
93}
94
95
96void fakefile_peer_close(struct fakefile_peer *peer)
97{
98    (void) close(peer->in);
99    (void) close(peer->out);
100    free(peer);
101}
102
103
104int fakefile_peer_fd(const struct fakefile_peer *peer)
105{
106    return peer->in;
107}
108
109
110struct fakefile_msg *fakefile_msg_new(struct fakefile_peer *peer, int size)
111{
112    struct fakefile_msg *msg;
113    size_t buf_size;
114
115    size += sizeof(int);
116    buf_size = size > BUF_SIZE ? BUF_SIZE : size;
117    msg = alloc_size(sizeof(struct fakefile_msg)+buf_size);
118    msg->peer = sanitize_peer(peer);
119    msg->buf = msg->pos = msg+1;
120    msg->len = 0;
121    msg->msg_size = size;
122    msg->buf_size = buf_size;
123    fakefile_msg_add_int(msg, size);
124    return msg;
125}
126
127
128static void flush_out(struct fakefile_msg *msg)
129{
130    const void *p;
131    ssize_t len;
132
133    if (msg->pos == msg->buf)
134        return;
135    for (p = msg->buf; p != msg->pos; p += len) {
136        len = write(msg->peer->out, p, msg->pos-p);
137        if (len <= 0) {
138            perror("fakefile IPC write");
139            exit(1);
140        }
141    }
142}
143
144
145struct fakefile_msg *fakefile_msg_recv(struct fakefile_peer *peer)
146{
147    struct fakefile_msg *msg;
148
149    msg = alloc_type(struct fakefile_msg);
150    msg->peer = sanitize_peer(peer);
151    msg->buf = NULL;
152    msg->len = 0;
153    msg->msg_size = sizeof(int);
154    msg->msg_size = fakefile_msg_get_int(msg);
155    return msg;
156}
157
158
159void fakefile_msg_end(struct fakefile_msg *msg)
160{
161#if 0
162fprintf(stderr, "end: len %d size %d (%p)\n",
163  (int) msg->len, (int) msg->msg_size, msg->buf);
164#endif
165    assert(msg->len == msg->msg_size);
166    if (msg->buf)
167        flush_out(msg);
168    free(msg);
169}
170
171
172static void add_chunk(struct fakefile_msg *msg, const void *buf, size_t len)
173{
174    memcpy(msg->pos, buf, len);
175    msg->pos += len;
176    if (msg->pos == msg->buf+msg->buf_size) {
177        flush_out(msg);
178        msg->pos = msg->buf;
179    }
180}
181
182
183void fakefile_msg_add(struct fakefile_msg *msg, const void *buf, size_t len)
184{
185    size_t chunk;
186
187#if 0
188fprintf(stderr, "add: %d+%d/%d (%p)\n",
189    (int) msg->len, (int) len, (int) msg->msg_size, msg->buf);
190#endif
191    assert(msg->len+len <= msg->msg_size);
192    while (len && msg->pos+len > msg->buf+msg->buf_size) {
193        chunk = msg->buf+msg->buf_size-msg->pos;
194        if (chunk > len)
195            chunk = len;
196        add_chunk(msg, buf, chunk);
197        buf += chunk;
198        len -= chunk;
199        msg->len += chunk;
200    }
201    if (len) {
202        add_chunk(msg, buf, len);
203        msg->len += len;
204    }
205}
206
207
208static size_t get_chunk(struct fakefile_peer *peer, void *buf, size_t len)
209{
210    ssize_t got;
211
212    got = read(peer->in, buf, len);
213    if (got < 0) {
214        perror("fakefile IPC read");
215        exit(1);
216    }
217    if (!got) {
218        fprintf(stderr, "fakefile EOF\n");
219        exit(1);
220    }
221    return got;
222}
223
224
225void fakefile_msg_get(struct fakefile_msg *msg, void *buf, size_t len)
226{
227    struct fakefile_peer *peer = msg->peer;
228    size_t chunk, got;
229
230    assert(msg->len+len <= msg->msg_size);
231    if (!len)
232        return;
233    if (peer->pos != peer->end) {
234        chunk = peer->end-peer->pos;
235        if (chunk > len)
236            chunk = len;
237        memcpy(buf, peer->pos, chunk);
238        peer->pos += chunk;
239        buf += chunk;
240        len -= chunk;
241        msg->len += chunk;
242    }
243    while (len >= BUF_SIZE) {
244        got = get_chunk(peer, buf, BUF_SIZE);
245        buf += got;
246        len -= got;
247        msg->len += got;
248    }
249    if (!len)
250        return;
251    peer->pos = peer->buf;
252    peer->end = peer->buf+get_chunk(peer, peer->buf, BUF_SIZE);
253    fakefile_msg_get(msg, buf, len);
254}
255

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