util: Replace state with separate booleans in extract_first_word

This simplifies the logic and uniformizes the way single and double
quotes are handled. In the end, the code is about 40 lines shorter.

Tested by running the excellent test cases from test-util. Also
installed the systemd binaries including this patch and booted a
system with it, everything looked normal.

1 files changed, 50 insertions, 89 deletions

diff --git a/src/basic/util.c b/src/basic/util.c
index 3989b415fa..d782bc6bdd 100644
--- a/src/basic/util.c
+++ b/src/basic/util.c
@@ -5815,16 +5815,10 @@ int extract_first_word(const char **p, char **ret, const char *separators, Extra
         size_t allocated = 0, sz = 0;
         int r;
 
-        enum {
-                START,
-                VALUE,
-                VALUE_ESCAPE,
-                SINGLE_QUOTE,
-                SINGLE_QUOTE_ESCAPE,
-                DOUBLE_QUOTE,
-                DOUBLE_QUOTE_ESCAPE,
-                SEPARATOR,
-        } state = START;
+        char quote = 0;                 /* 0 or ' or " */
+        bool backslash = false;         /* whether we've just seen a backslash */
+        bool separator = false;         /* whether we've just seen a separator */
+        bool start = true;              /* false means we're looking at a value */
 
         assert(p);
         assert(ret);
@@ -5844,9 +5838,7 @@ int extract_first_word(const char **p, char **ret, const char *separators, Extra
         for (;;) {
                 char c = **p;
 
-                switch (state) {
-
-                case START:
+                if (start) {
                         if (flags & EXTRACT_DONT_COALESCE_SEPARATORS)
                                 if (!GREEDY_REALLOC(s, allocated, sz+1))
                                         return -ENOMEM;
@@ -5854,11 +5846,10 @@ int extract_first_word(const char **p, char **ret, const char *separators, Extra
                         if (c == 0)
                                 goto finish_force_terminate;
                         else if (strchr(separators, c)) {
-                                if (flags & EXTRACT_DONT_COALESCE_SEPARATORS) {
-                                        (*p) ++;
+                                (*p) ++;
+                                if (flags & EXTRACT_DONT_COALESCE_SEPARATORS)
                                         goto finish_force_next;
-                                }
-                                break;
+                                continue;
                         }
 
                         /* We found a non-blank character, so we will always
@@ -5867,78 +5858,16 @@ int extract_first_word(const char **p, char **ret, const char *separators, Extra
                         if (!GREEDY_REALLOC(s, allocated, sz+1))
                                 return -ENOMEM;
 
-                        state = VALUE;
-                        /* fallthrough */
-
-                case VALUE:
-                        if (c == 0)
-                                goto finish_force_terminate;
-                        else if (c == '\'' && (flags & EXTRACT_QUOTES))
-                                state = SINGLE_QUOTE;
-                        else if (c == '\\')
-                                state = VALUE_ESCAPE;
-                        else if (c == '\"' && (flags & EXTRACT_QUOTES))
-                                state = DOUBLE_QUOTE;
-                        else if (strchr(separators, c)) {
-                                if (flags & EXTRACT_DONT_COALESCE_SEPARATORS) {
-                                        (*p) ++;
-                                        goto finish_force_next;
-                                }
-                                state = SEPARATOR;
-                        } else {
-                                if (!GREEDY_REALLOC(s, allocated, sz+2))
-                                        return -ENOMEM;
-
-                                s[sz++] = c;
-                        }
-
-                        break;
-
-                case SINGLE_QUOTE:
-                        if (c == 0) {
-                                if (flags & EXTRACT_RELAX)
-                                        goto finish_force_terminate;
-                                return -EINVAL;
-                        } else if (c == '\'')
-                                state = VALUE;
-                        else if (c == '\\')
-                                state = SINGLE_QUOTE_ESCAPE;
-                        else {
-                                if (!GREEDY_REALLOC(s, allocated, sz+2))
-                                        return -ENOMEM;
-
-                                s[sz++] = c;
-                        }
-
-                        break;
-
-                case DOUBLE_QUOTE:
-                        if (c == 0) {
-                                if (flags & EXTRACT_RELAX)
-                                        goto finish_force_terminate;
-                                return -EINVAL;
-                        } else if (c == '\"')
-                                state = VALUE;
-                        else if (c == '\\')
-                                state = DOUBLE_QUOTE_ESCAPE;
-                        else {
-                                if (!GREEDY_REALLOC(s, allocated, sz+2))
-                                        return -ENOMEM;
-
-                                s[sz++] = c;
-                        }
-
-                        break;
+                        start = false;
+                }
 
-                case SINGLE_QUOTE_ESCAPE:
-                case DOUBLE_QUOTE_ESCAPE:
-                case VALUE_ESCAPE:
+                if (backslash) {
                         if (!GREEDY_REALLOC(s, allocated, sz+7))
                                 return -ENOMEM;
 
                         if (c == 0) {
                                 if ((flags & EXTRACT_CUNESCAPE_RELAX) &&
-                                    (state == VALUE_ESCAPE || flags & EXTRACT_RELAX)) {
+                                    (!quote || flags & EXTRACT_RELAX)) {
                                         /* If we find an unquoted trailing backslash and we're in
                                          * EXTRACT_CUNESCAPE_RELAX mode, keep it verbatim in the
                                          * output.
@@ -5977,17 +5906,49 @@ int extract_first_word(const char **p, char **ret, const char *separators, Extra
                                 s[sz++] = c;
 
 end_escape:
-                        state = (state == SINGLE_QUOTE_ESCAPE) ? SINGLE_QUOTE :
-                                (state == DOUBLE_QUOTE_ESCAPE) ? DOUBLE_QUOTE :
-                                VALUE;
-                        break;
+                        backslash = false;
+
+                } else if (quote) {     /* inside either single or double quotes */
+                        if (c == 0) {
+                                if (flags & EXTRACT_RELAX)
+                                        goto finish_force_terminate;
+                                return -EINVAL;
+                        } else if (c == quote)          /* found the end quote */
+                                quote = 0;
+                        else if (c == '\\')
+                                backslash = true;
+                        else {
+                                if (!GREEDY_REALLOC(s, allocated, sz+2))
+                                        return -ENOMEM;
+
+                                s[sz++] = c;
+                        }
 
-                case SEPARATOR:
+                } else if (separator) {
                         if (c == 0)
                                 goto finish_force_terminate;
                         if (!strchr(separators, c))
                                 goto finish;
-                        break;
+
+                } else {
+                        if (c == 0)
+                                goto finish_force_terminate;
+                        else if ((c == '\'' || c == '"') && (flags & EXTRACT_QUOTES))
+                                quote = c;
+                        else if (c == '\\')
+                                backslash = true;
+                        else if (strchr(separators, c)) {
+                                if (flags & EXTRACT_DONT_COALESCE_SEPARATORS) {
+                                        (*p) ++;
+                                        goto finish_force_next;
+                                }
+                                separator = true;
+                        } else {
+                                if (!GREEDY_REALLOC(s, allocated, sz+2))
+                                        return -ENOMEM;
+
+                                s[sz++] = c;
+                        }
                 }
 
                 (*p) ++;