Initial commit, 2 years later

1 files changed, 543 insertions, 0 deletions

diff --git a/c/sources/ezipc.h b/c/sources/ezipc.h
new file mode 100644
index 0000000..ff69fe1
--- /dev/null
+++ b/c/sources/ezipc.h
@@ -0,0 +1,543 @@
+/*
+ * BSD 3-Clause License (BSD-3-Clause)
+ *
+ * Copyright (C) 2022 - dweller <dweller@cabin.digital>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * 3. Neither the name of the copyright holder nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+
+/*
+ *                                    EZIPC
+ *          EZ(easy) Inter-Process Communication single-file library
+ *
+ *
+ * At the moment, this is just a wrapper around POSIX named pipes (aka FIFOs)
+ * that creates duplex communication channel between 2 processes.
+ *
+ *
+ *                              Brief Description
+ *
+ * Just create the connections with ezi_create() on a "server" and ezi_connect()
+ * on a "client" process. Then use ezi_{send,recv}() functions to push data
+ * around. There is no functional difference between "server" and "client"
+ * except that "server" is ultimately responsible for OS resources (the created
+ * named pipes) clean up.
+ * When you're done, ezi_destroy() the connection on the "server" and
+ * ezi_disconnect() it on the "client" side.
+ *
+ * The library provides a reliable way to send sized frames between 2 processes.
+ * The data size is enforced, but other than that there are no assumptions about
+ * possible higher-level usage of this code. If the reader cannot receive full
+ * frame at once, it is truncated and the reset is discarded. Send and receive
+ * failures are considered fatal and restart (disconnected, reconnect) of the
+ * connection is required.
+ *
+ * All functions are blocking on their specific action. Create/Connect wait for
+ * the other end of the connection, send waits for there to be room in the OS
+ * buffers, recv waits for something to read from OS buffers.
+ *
+ * While more than 2 process are able to read from same connection
+ * (read: named pipes), THIS IS *HIGHLY* INADVISABLE, as there are no guarantees
+ * about data interleaving in such case.
+ *
+ *
+ *                             Single-file Usage
+ *
+ * Define "EZIPC_IMPL" before this header inclusion into any *.c file to get
+ * the implementation code injected into said .c file. Compile and run.
+ *
+ *
+ *                                 Examples
+ *
+ * See files server.c, client.c, and common.h for a simple usage example.
+ *
+ *
+ *                               Symbol List
+ *
+ * EZIPC_VERSION
+ *
+ * typedef struct ezi_conn_s ezi_conn
+ *
+ * ezi_conn* ezi_create(const char* conn_path)
+ * void ezi_destroy(ezi_conn* conn)
+ *
+ * ezi_conn* ezi_connect(const char* conn_path)
+ * void ezi_disconnect(ezi_conn* conn)
+ *
+ * bool ezi_send(ezi_conn* conn, const void* data, size_t size)
+ * bool ezi_recv(ezi_conn* conn, void* data, size_t* size);
+ *
+ * See bellow for specific function descriptions.
+ *
+ *
+ *                                Compliance
+ *
+ * This code adheres to C99 standard, and was tested with following command:
+ * > $ gcc -std=c99 -Wall -Wextra -pedantic
+ *
+ *
+ *                               Known Issues
+ *
+ *  1. When "server" abruptly disconnects "client" gets SIGPIPE "broken pipe"
+ *     signal, which is annoying because it would be way better to just return
+ *     false from last called function and perror() for information.
+ *
+ *     Workaround: "client" can insert a signal handler and have a callback, or
+ *                 accept quick death as a positive.
+ *
+ *
+ *                                 Changelog
+ *
+ * v1.2 - ezi_recv() now fails on receiving a size of 0 bytes
+ * v1.1 - C++ support (extern and void* casts)
+ * v1   - release
+ */
+
+
+#ifndef EZIPC_H
+#define EZIPC_H
+
+
+#define EZIPC_VERSION "v1.2"
+
+
+#include <stddef.h>
+#include <stdbool.h>
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+/*
+ * Opaque pointer to the structure representing the connection.
+ */
+typedef struct ezi_conn_s ezi_conn;
+
+
+/*
+ * Creates the "server" (controlling/initial) end of the connection. This end
+ * of the connection may create underlying OS resources if they do not exist,
+ * AND IS responsible for cleaning them.
+ * resources.
+ *
+ * BLOCKS: waits for other end to connect.
+ *
+ * Arguments:
+ *   IN `conn_path` - path to store the implementation-related resources,
+ *                    doubles as a connection identifier.
+ *
+ * Returns the connection object as an opaque pointer.
+ */
+extern ezi_conn* ezi_create(const char* conn_path);
+
+/*
+ * Destroys the connection and frees the underlying OS resources if connection
+ * was established with `ezi_create()` function.
+ *
+ * Arguments:
+ *   IN `conn` - connection object that represents the connection.
+ *
+ *  Returns: nothing.
+ */
+extern void ezi_destroy(ezi_conn* conn);
+
+/*
+ * Creates the "client" end of the connection. This end of the connection may
+ * create underlying OS resources if they do not exist, but IS NOT responsible
+ * for them.
+ *
+ * BLOCKS: waits for other end to connect.
+ *
+ * Arguments:
+ *   IN `conn_path` - path to store the implementation-related resources,
+ *                    doubles as a connection identifier.
+ *
+ * Returns the connection object as an opaque pointer.
+ */
+
+extern ezi_conn* ezi_connect(const char* conn_path);
+
+/*
+ * Destroys the connection and frees the underlying OS resources if connection
+ * was established with `ezi_create()` function.
+ * Is an alias of `ezi_destroy`. Exists for symmetry in the API.
+ *
+ * Arguments:
+ *   IN `conn` - connection object that represents the connection.
+ *
+ *  Returns: nothing.
+ */
+#define ezi_disconnect(conn) ezi_destroy(conn)
+
+
+/*
+ * Sends `size` bytes to the other endpoint.
+ *
+ * BLOCKS: waits for room in the underlying buffer.
+ *
+ * Arguments:
+ *   IN `conn` - connection object that represents the connection.
+ *   IN `data` - buffer of `size` bytes to be sent.
+ *   IN `size` - size of the data to be sent, in bytes.
+ *
+ * Returns: true on success, false on failure. If failed, the connection is
+ *          thought to be in undefined state and has to be closed and reopened
+ *          for communication to continue.
+ */
+extern bool ezi_send(ezi_conn* conn, const void* data, size_t size);
+
+/*
+ * Receives up to `size` bytes from the other endpoint. If there is more data
+ * available that `size`, it is *discarded*!
+ *
+ * BLOCKS: waits for data in the underlying buffer.
+ *
+ * Arguments:
+ *   IN    `conn` - connection object that represents the connection.
+ *   OUT   `data` - buffer of `size` bytes to be filled with incoming data;
+ *                  on success holds the received data, which may be truncated
+ *                       to the input `size`;
+ *                  on failure data is undefined.
+ *   INOUT `size` - as an input: specifies the size of `data` buffer in bytes;
+ *                  as an output:
+ *                    on success holds the size of the received data, which may
+ *                          be smaller than the `data` buffer size passed as an
+ *                          input;
+ *                    on failure is unchanged from input.
+ *
+ * Returns: true on success, false on failure. If failed, the connection is
+ *          thought to be in undefined state and has to be closed and reopened
+ *          for communication to continue.
+ */
+extern bool ezi_recv(ezi_conn* conn, void* data, size_t* size);
+
+#ifdef __cplusplus
+}
+#endif // EXTERN C
+
+
+#endif // EZIPC_H
+
+
+//
+// =========================================================================
+//
+// What follows are implementation details
+//
+//
+
+#ifdef EZIPC_IMPL
+#ifndef EZIPC_IMPLEMENTED
+#define EZIPC_IMPLEMENTED // redefinition guard
+#ifdef __linux__
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+#include <stdint.h>
+
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+struct ezi_conn_s
+{
+    char* path_c2s;
+    char* path_s2c;
+    int c2s, s2c;
+
+    bool server;
+};
+
+
+static ezi_conn* _ezi_internal_create(const char* conn_path,
+                                      const mode_t modes[2])
+{
+    if(!conn_path) return NULL;
+
+    ezi_conn* conn = (ezi_conn*)calloc(1, sizeof(*conn));
+    if(!conn) return NULL;
+
+    conn->c2s = -1;
+    conn->s2c = -1;
+
+    // Populate path strings
+    {
+        const size_t path_len = strlen(conn_path);
+
+        conn->path_c2s = (char*)malloc(path_len + 5);
+        if(!conn->path_c2s) goto cleanup;
+
+        strcat(conn->path_c2s, conn_path);
+        strcat(conn->path_c2s, "_c2s");
+
+        conn->path_s2c = (char*)malloc(path_len + 5);
+        if(!conn->path_s2c) goto cleanup;
+
+        strcat(conn->path_s2c, conn_path);
+        strcat(conn->path_s2c, "_s2c");
+    }
+
+
+    // Create POSIX FIFOs
+    {
+        if(mkfifo(conn->path_c2s, 0660) != 0)
+        {
+            if(errno != EEXIST)
+            {
+                perror("[EZIPC] Could not create client->server pipe");
+                goto cleanup;
+            }
+        }
+
+        if(mkfifo(conn->path_s2c, 0660) != 0)
+        {
+            if(errno != EEXIST)
+            {
+                perror("[EZIPC] Could not create server->client pipe");
+                goto cleanup;
+            }
+        }
+    }
+
+    // Open the FIFOs
+    {
+        conn->c2s = open(conn->path_c2s, modes[0]);
+        if(conn->c2s < 0)
+        {
+            perror("[EZIPC] Could not open client->server pipe");
+            goto cleanup;
+        }
+
+        conn->s2c = open(conn->path_s2c, modes[1]);
+        if(conn->s2c < 0)
+        {
+            perror("[EZIPC] Could not open server->client pipe");
+            goto cleanup;
+        }
+    }
+
+    return conn;
+
+cleanup:
+
+    if(conn)
+    {
+        ezi_destroy(conn);
+
+        if(conn->path_c2s) free(conn->path_c2s);
+        if(conn->path_s2c) free(conn->path_s2c);
+
+        free(conn);
+    }
+
+    return NULL;
+}
+
+
+ezi_conn* ezi_create(const char* conn_path)
+{
+    const mode_t modes[2] = { O_RDONLY, O_WRONLY};
+
+    ezi_conn* conn = _ezi_internal_create(conn_path, modes);
+    if(conn) conn->server = true;
+
+    return conn;
+}
+
+ezi_conn* ezi_connect(const char* conn_path)
+{
+    const mode_t modes[2] = { O_WRONLY, O_RDONLY};
+
+    ezi_conn* conn = _ezi_internal_create(conn_path, modes);
+    if(conn) conn->server = false;
+
+    return conn;
+}
+
+void ezi_destroy(ezi_conn* conn)
+{
+    if(!conn) return;
+
+    // NOTE: even if close() errors out, DO NOT retry (even if EINTR) as per
+    //       man 2 close. Just report the error and clobber the FDs.
+
+    if(conn->c2s >= 0)
+    {
+        int rc = close(conn->c2s);
+        if(rc < 0) perror("[EZIPC] Could not close client->server pipe");
+
+        conn->c2s = -1;
+    }
+
+    if(conn->s2c >= 0)
+    {
+        int rc = close(conn->s2c);
+        if(rc < 0) perror("[EZIPC] Could not close server->client pipe");
+
+        conn->s2c = -1;
+    }
+
+    // I could check and handle remove error here, but I'd rather tell the user
+    // and not accidentally delete something else
+
+    if(conn->server)
+    {
+        if(conn->path_c2s && (remove(conn->path_c2s) != 0))
+            perror("[EZIPC] Could not delete client->server pipe");
+
+        if(conn->path_s2c && (remove(conn->path_s2c) != 0))
+            perror("[EZIPC] Could not delete server->client pipe");
+    }
+}
+
+// wrapper over write() to handle interrupted syscall
+static bool _ezi_write(int ep, const void* buffer, size_t size)
+{
+    const uint8_t* bytes = (uint8_t*)buffer;
+
+    size_t written = 0;
+    while(written < size)
+    {
+        size_t got = write(ep, bytes + written, size - written);
+        if(got <= 0)// FIXME: technically < 0 but I don't want an infinite loop
+        {
+            perror("[EZIPC] Could not write to pipe");
+            return false;
+        }
+
+        written += size;
+    }
+
+    return true;
+}
+
+
+bool ezi_send(ezi_conn* conn, const void* data, size_t size)
+{
+    if(!conn) return false;
+    if(!data) return false;
+    if(size == 0) return true;
+
+    const int ep = conn->server ? conn->s2c : conn->c2s;
+    if(ep >= 0)
+    {
+        const uint64_t out_size = (uint64_t)size;
+        if(!_ezi_write(ep, &out_size, sizeof(out_size))) return false;
+        if(!_ezi_write(ep, data, size)) return false;
+
+        return true;
+    }
+    else return false;
+
+}
+
+// wrapper over read() to handle interrupted syscall
+static bool _ezi_read(int ep, void* buffer, size_t size)
+{
+    uint8_t* bytes = (uint8_t*)buffer;
+
+    size_t readback = 0;
+    while(readback < size)
+    {
+        ssize_t got = read(ep, bytes + readback, size - readback);
+        if(got == 0)
+        {
+            // NOTE: I think reading 0 bytes in non-blocking mode is fine,
+            //       but since I don't provide non-blocking mode, this is
+            //       still an error.
+            return false;
+        }
+        else if(got < 0)
+        {
+            perror("[EZIPC] Could not read from pipe");
+            return false;
+        }
+
+        readback += got;
+    }
+
+    return true;
+}
+
+
+bool ezi_recv(ezi_conn* conn, void* data, size_t* size)
+{
+    if(!conn) return false;
+    if(!data) return false;
+    if(!size) return false;
+    if(*size == 0) return true;
+
+    const int ep = conn->server ? conn->c2s : conn->s2c;
+    if(ep >= 0)
+    {
+        // NOTE: since this is IPC, we're on the same machine so no need to
+        //       ensure endianness
+        uint64_t in_size = 0;
+        if(!_ezi_read(ep, &in_size, sizeof(in_size))) return false;
+
+        if(in_size == 0) return false;
+
+        const uint64_t read_size = in_size > *size ? *size : in_size;
+        if(!_ezi_read(ep, data, read_size)) return false;
+
+        // If we have left over, get rid of it to guarantee correct read next
+        // time
+        for(uint64_t i = 0; i < (in_size - read_size); i++)
+        {
+            uint8_t temp; // I know I could read in bigger chunks, but honestly
+                          // I don't care, and assume this is an edge case
+            if(!_ezi_read(ep, &temp, 1)) return false;
+        }
+
+        *size = read_size;
+        return true;
+
+    } else return false;
+
+}
+
+#ifdef __cplusplus
+}
+#endif // EXTERN C
+
+#else // __linux__
+    #error "EZ IPC library is not supported on your platform. Want to port?"
+#endif // platforms
+#endif // EZIPC_IMPLEMENTED
+#endif // EZIPC_IMPL