Make request parsing reentrant

client.c

@@ -34,22 +34,6 @@ bool char_to_hex_digit(char in, char *out) {
     return true;
 }
 
-bool hex_digit_to_char(char in, char *out) {
-    if (in >= '0' && in <= '9') {
-        *out = in - '0';
-        return true;
-    }
-    if (in >= 'a' && in <= 'f') {
-        *out = in - 'a' + 10;
-        return true;
-    }
-    if (in >= 'A' && in <= 'F') {
-        *out = in - 'A' + 10;
-        return true;
-    }
-    return false;
-}
-
 bool char_to_hex_digits(char in, char *hi, char *lo) {
     return char_to_hex_digit((in & 0xf0) >> 4, hi)
         && char_to_hex_digit(in & 0x0f, lo);
@@ -62,106 +46,6 @@ void rdb_client_init(RdbClient *self, int connfd) {
     self->should_ack = true;
 }
 
-#define BUFFER_LEN 8096
-
-typedef struct Buffer {
-    char buf[BUFFER_LEN];
-    size_t len;
-    size_t index;
-} Buffer;
-
-static Buffer INBUF = {
-    .len = 0,
-    .index = 0,
-};
-
-static ssize_t read_next_char(int connfd, char *in) {
-    if (INBUF.index >= INBUF.len) {
-        ssize_t inlen = read(connfd, INBUF.buf, BUFFER_LEN);
-        if (inlen < 1) {
-            // either we got an error (-1) or the connection closed (0)
-            return inlen;
-        }
-        INBUF.index = 0;
-        INBUF.len = inlen;
-    }
-    *in = INBUF.buf[INBUF.index++];
-    return 1;
-}
-
-ssize_t rdb_client_read(RdbClient *self, char *buf, size_t len) {
-    // read any acknowledgements and continue
-    char in;
-    do {
-        ssize_t res = read_next_char(self->connfd, &in);
-        if (res < 1) return res;
-    } while (in == '+');
-
-    if (in == '\x03') {
-        // interrupt from the server
-        *buf = in;
-        return 1;
-    }
-
-    if (in == '-') {
-        // we don't handle resending right now
-        return -1;
-    }
-
-    // now, expect to be at the start of a packet
-    if (in != '$') {
-        fprintf(stderr, "unexpected packet start \"%c\"", in);
-        return -1;
-    }
-
-    size_t outlen = 0;
-    char chk = 0;
-    while (1) {
-        ssize_t res = read_next_char(self->connfd, &in);
-        if (res < 1) return res;
-
-        if (in == '#') {
-            // end of packet, checksum next
-            break;
-        }
-        if (outlen >= len) {
-            // ran out of room in the buffer
-            fprintf(stderr, "packet too big for buffer\n");
-            return -1;
-        }
-        if (in == '}') {
-            // escape sequence
-            chk += in;
-            res = read_next_char(self->connfd, &in);
-            if (res < 1) return res;
-            chk += in;
-            buf[outlen++] = in ^ 0x20;
-        } else {
-            chk += in;
-            buf[outlen++] = in;
-        }
-    };
-
-    // validate the checksum
-    char hi, lo;
-
-    ssize_t res = read_next_char(self->connfd, &in);
-    if (res < 1) return res;
-    if (!hex_digit_to_char(in, &hi)) return -1;
-
-    res = read_next_char(self->connfd, &in);
-    if (res < 1) return res;
-    if (!hex_digit_to_char(in, &lo)) return -1;
-
-    char real_chk = (hi << 4) | lo;
-    if (real_chk != chk) {
-        fprintf(stderr, "invalid checksum\n");
-        return -1;
-    }
-
-    return outlen;
-}
-
 void rdb_client_begin_packet(RdbClient *self) {
     self->len = 0;
     self->chk = 0;

cmdbuf.c

@@ -1,4 +1,5 @@
 #include <cmdbuf.h>
+#include <hex.h>
 #include <string.h>
 
 bool cmd_match_str(CommandBuf *cmd, const char *str) {
@@ -23,22 +24,6 @@ bool cmd_match_only_str(CommandBuf *cmd, const char *str) {
     return false;
 }
 
-static bool parse_hex_digit(char digit, char *out) {
-    if (digit >= '0' && digit <= '9') {
-        *out = digit - '0';
-        return true;
-    }
-    if (digit >= 'a' && digit <= 'f') {
-        *out = digit - 'a' + 10;
-        return true;
-    }
-    if (digit >= 'A' && digit <= 'F') {
-        *out = digit - 'A' + 10;
-        return true;
-    }
-    return false;
-}
-
 bool cmd_match_hex_number(CommandBuf *cmd, uint32_t *value) {
     size_t read = 0;
     size_t max_len = cmd->len;

hex.c

@@ -0,0 +1,17 @@
+#include <hex.h>
+
+bool parse_hex_digit(char digit, char *out) {
+    if (digit >= '0' && digit <= '9') {
+        *out = digit - '0';
+        return true;
+    }
+    if (digit >= 'a' && digit <= 'f') {
+        *out = digit - 'a' + 10;
+        return true;
+    }
+    if (digit >= 'A' && digit <= 'F') {
+        *out = digit - 'A' + 10;
+        return true;
+    }
+    return false;
+}

include/client.h

@@ -17,7 +17,6 @@ typedef struct RdbClient {
 } RdbClient;
 
 void rdb_client_init(RdbClient *self, int connfd);
-ssize_t rdb_client_read(RdbClient *self, char *buf, size_t len);
 void rdb_client_begin_packet(RdbClient *self);
 bool rdb_client_write_str(RdbClient *self, const char *str);
 bool rdb_client_write_str_hex(RdbClient *self, const char *str);

include/hex.h

@@ -0,0 +1,8 @@
+#ifndef V810_HEX_H_
+#define V810_HEX_H_
+
+#include <stdbool.h>
+
+bool parse_hex_digit(char digit, char *out);
+
+#endif

include/request.h

@@ -0,0 +1,41 @@
+#ifndef RDBSERVER_REQUEST_H
+#define RDBSERVER_REQUEST_H
+
+#include <stddef.h>
+
+#define INBUF_LEN 256
+
+typedef enum rdb_read_result_t {
+    read_result_success,
+    read_result_error,
+    read_result_pending,
+    read_result_disconnected,
+} rdb_read_result_t;
+
+typedef enum rdb_read_state_t {
+    read_state_header,
+    read_state_body,
+    read_state_body_escape,
+    read_state_checksum_1,
+    read_state_checksum_2,
+} rdb_read_state_t;
+
+typedef struct RdbRequest {
+    int connfd;
+    struct Buffer {
+        char buf[INBUF_LEN];
+        size_t len;
+        size_t index;
+    } inbuf;
+    rdb_read_state_t state;
+    char *cmd;
+    size_t cmdlen;
+    size_t outlen;
+    char chk;
+} RdbRequest;
+
+void rdb_request_init(RdbRequest *req, int connfd, char *cmd, size_t cmdlen);
+void rdb_request_reset(RdbRequest *req);
+rdb_read_result_t rdb_request_read(RdbRequest *req, size_t *len);
+
+#endif

main.c

@@ -1,5 +1,6 @@
 #include <client.h>
 #include <cmdbuf.h>
+#include <request.h>
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -209,24 +210,30 @@ int handle_command(RdbClient *client, CommandBuf *cmd, VB *sim) {
         }
         return rdb_client_send_packet(client);
     }
-    fprintf(stderr, "Unrecognized command.");
+    fprintf(stderr, "Unrecognized command.\n");
     return rdb_client_send_packet(client);
 }
 
 
 int server(int connfd, VB *sim) {
+    RdbRequest req;
     RdbClient client;
+    char buf[BUFLEN];
+    size_t len;
+
+    rdb_request_init(&req, connfd, buf, BUFLEN);
     rdb_client_init(&client, connfd);
 
-    char buf[BUFLEN];
     while (1) {
-        ssize_t len = rdb_client_read(&client, buf, BUFLEN);
-        if (len < 0) {
-            perror("could not read data");
-            return -len;
-        } else if (len == 0) {
+        rdb_read_result_t result = rdb_request_read(&req, &len);
+        if (result == read_result_error) {
+            return -1;
+        } else if (result == read_result_disconnected) {
             printf("client has disconnected\n");
             return 0;
+        } else if (result == read_result_pending) {
+            // TODO: should run the emulator while we wait
+            continue;
         } else {
             printf("received command \"%.*s\"\n", (int) len, buf);
             fflush(stdout);
@@ -237,7 +244,7 @@ int server(int connfd, VB *sim) {
             if (res != 0) {
                 return res;
             }
-            // +$QStartNoAckMode#b0
+            rdb_request_reset(&req);
         }
 
     }

makefile

@@ -1,6 +1,6 @@
 build:
 	@mkdir -p build
-	@gcc main.c client.c cmdbuf.c ../vbtest/vb.c -I include -I ../vbtest \
+	@gcc main.c client.c cmdbuf.c hex.c request.c ../vbtest/vb.c -I include -I ../vbtest \
 	-Werror -Wall -Wextra -Wpedantic \
 	-Wno-unused-parameter -Wno-unused-function \
 	-o ./build/rdb

request.c

@@ -0,0 +1,146 @@
+#include <errno.h>
+#include <hex.h>
+#include <request.h>
+#include <stdio.h>
+#include <unistd.h>
+
+void rdb_request_init(RdbRequest *req, int connfd, char *cmd, size_t cmdlen) {
+    req->connfd = connfd;
+    req->cmd = cmd;
+    req->cmdlen = cmdlen;
+    rdb_request_reset(req);
+}
+
+void rdb_request_reset(RdbRequest *req) {
+    req->state = read_state_header;
+    req->inbuf.len = 0;
+    req->inbuf.index = 0;
+    req->outlen = 0;
+    req->chk = 0;
+}
+
+static rdb_read_result_t read_char(RdbRequest *req, char *in) {
+    if (req->inbuf.index >= req->inbuf.len) {
+        ssize_t inlen = read(req->connfd, req->inbuf.buf, INBUF_LEN);
+        if (inlen == 0) {
+            return read_result_disconnected;
+        }
+        if (inlen < 0) {
+            if (errno == EAGAIN) {
+                return read_result_pending;
+            } else {
+                perror("could not read incoming packet");
+                return read_result_error;
+            }
+        }
+        req->inbuf.index = 0;
+        req->inbuf.len = inlen;
+    }
+    *in = req->inbuf.buf[req->inbuf.index++];
+    return read_result_success;
+}
+
+rdb_read_result_t rdb_request_read(RdbRequest *req, size_t *len) {
+    rdb_read_result_t res;
+    char in;
+
+    switch (req->state) {
+    case read_state_header:
+        // read any acknowledgements and continue
+        do {
+            res = read_char(req, &in);
+            if (res != read_result_success) return res;
+        } while (in == '+');
+
+        if (in == '-') {
+            fprintf(stderr, "negative ack not supported\n");
+            return read_result_error;
+        }
+
+        if (in == '\x03') {
+            // interrupt from the server
+            req->cmd[0] = in;
+            req->outlen = 1;
+            return read_result_success;
+        }
+
+        // now, we should be at the start of a packet
+        if (in != '$') {
+            fprintf(stderr, "unexpected packet start \"%c\"\n", in);
+            return read_result_error;
+        }
+
+        req->state = read_state_body;
+        __attribute__ ((fallthrough));
+    case read_state_body:
+    case read_state_body_escape:
+        while (1) {
+            res = read_char(req, &in);
+            if (res != read_result_success) return res;
+
+            if (req->state == read_state_body && in == '#') {
+                // end of packet body
+                break;
+            }
+
+            req->chk += in;
+
+            if (req->state == read_state_body && in == '}') {
+                // escape sequence
+                req->state = read_state_body_escape;
+                continue;
+            }
+
+            if (req->outlen >= req->cmdlen) {
+                // ran out of room in the buffer
+                fprintf(stderr, "packet too big for buffer\n");
+                return read_result_error;
+            }
+
+            if (req->state == read_state_body_escape) {
+                req->cmd[req->outlen++] = in ^ 0x20;
+                req->state = read_state_body;
+            } else {
+                req->cmd[req->outlen++] = in;
+            }
+        }
+        req->state = read_state_checksum_1;
+        __attribute__ ((fallthrough));
+    case read_state_checksum_1:
+        res = read_char(req, &in);
+        if (res != read_result_success) return res;
+
+        // check the high digit of the checksum
+        char hi;
+        if (!parse_hex_digit(in, &hi)) {
+            fprintf(stderr, "invalid checksum1\n");
+            return read_result_error;
+        }
+        if (((req->chk >> 4) & 0x000f) != hi) {
+            fprintf(stderr, "invalid checksum2\n");
+            return read_result_error;
+        }
+        req->state = read_state_checksum_2;
+        __attribute__ ((fallthrough));
+    case read_state_checksum_2:
+        res = read_char(req, &in);
+        if (res != read_result_success) return res;
+
+        // check the high digit of the checksum
+        char lo;
+        if (!parse_hex_digit(in, &lo)) {
+            fprintf(stderr, "invalid checksum3 %c\n", in);
+            return read_result_error;
+        }
+        if ((req->chk & 0x000f) != lo) {
+            fprintf(stderr, "invalid checksum4\n");
+            return read_result_error;
+        }
+
+        *len = req->outlen;
+        return read_result_success;
+    default:
+        fprintf(stderr, "invalid state\n");
+        return read_result_error;
+    }
+}