path: root/src/UriCommon.c

/*
 * uriparser - RFC 3986 URI parsing library
 *
 * Copyright (C) 2007, Weijia Song <songweijia@gmail.com>
 * Copyright (C) 2007, Sebastian Pipping <sebastian@pipping.org>
 * All rights reserved.
 *
 * 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.
 */

/* What encodings are enabled? */
#include <uriparser/UriDefsConfig.h>
#if (!defined(URI_PASS_ANSI) && !defined(URI_PASS_UNICODE))
/* Include SELF twice */
#  ifdef URI_ENABLE_ANSI
#    define URI_PASS_ANSI 1
#    include "UriCommon.c"
#    undef URI_PASS_ANSI
#  endif
#  ifdef URI_ENABLE_UNICODE
#    define URI_PASS_UNICODE 1
#    include "UriCommon.c"
#    undef URI_PASS_UNICODE
#  endif
#else
#  ifdef URI_PASS_ANSI
#    include <uriparser/UriDefsAnsi.h>
#  else
#    include <uriparser/UriDefsUnicode.h>
#    include <wchar.h>
#  endif

#  ifndef URI_DOXYGEN
#    include <uriparser/Uri.h>
#    include "UriCommon.h"
#    include "UriSets.h"
#  endif

#  include <assert.h>
#  include <stddef.h>

/*extern*/ const URI_CHAR * const URI_FUNC(SafeToPointTo) = _UT("X");
/*extern*/ const URI_CHAR * const URI_FUNC(ConstPwd) = _UT(".");
/*extern*/ const URI_CHAR * const URI_FUNC(ConstParent) = _UT("..");

void URI_FUNC(ResetUri)(URI_TYPE(Uri) * uri) {
    if (uri == NULL) {
        return;
    }
    memset(uri, 0, sizeof(URI_TYPE(Uri)));
}

int URI_FUNC(FreeUriPath)(URI_TYPE(Uri) * uri, UriMemoryManager * memory) {
    assert(uri != NULL);
    assert(memory != NULL);

    if (uri->pathHead != NULL) {
        URI_TYPE(PathSegment) * segWalk = uri->pathHead;
        while (segWalk != NULL) {
            URI_TYPE(PathSegment) * const next = segWalk->next;
            if ((uri->owner == URI_TRUE)
                && (segWalk->text.first != segWalk->text.afterLast)) {
                memory->free(memory, (URI_CHAR *)segWalk->text.first);
            }
            segWalk->text.first = NULL;
            segWalk->text.afterLast = NULL;
            segWalk->next = NULL;
            memory->free(memory, segWalk);
            segWalk = next;
        }
        uri->pathHead = NULL;
        uri->pathTail = NULL;
    }

    return URI_SUCCESS;
}

/* Compares two text ranges for equal text content */
int URI_FUNC(CompareRange)(const URI_TYPE(TextRange) * a, const URI_TYPE(TextRange) * b) {
    int diff;
    ptrdiff_t lenA;
    ptrdiff_t lenB;

    /* NOTE: Both NULL means equal! */
    if ((a == NULL) || (b == NULL)) {
        return ((a == NULL) ? 0 : 1) - ((b == NULL) ? 0 : 1);
    }

    /* NOTE: Both NULL means equal! */
    if ((a->first == NULL) || (b->first == NULL)) {
        return ((a->first == NULL) ? 0 : 1) - ((b->first == NULL) ? 0 : 1);
    }

    lenA = a->afterLast - a->first;
    lenB = b->afterLast - b->first;

    if (lenA > lenB) {
        return 1;
    } else if (lenA < lenB) {
        return -1;
    }

    diff = URI_STRNCMP(a->first, b->first, (size_t)lenA);

    if (diff > 0) {
        return 1;
    } else if (diff < 0) {
        return -1;
    }

    return diff;
}

UriBool URI_FUNC(CopyRange)(URI_TYPE(TextRange) * destRange,
                            const URI_TYPE(TextRange) * sourceRange,
                            UriMemoryManager * memory) {
    const int lenInChars = (int)(sourceRange->afterLast - sourceRange->first);
    const int lenInBytes = lenInChars * sizeof(URI_CHAR);
    URI_CHAR * dup = memory->malloc(memory, lenInBytes);
    if (dup == NULL) {
        return URI_FALSE;
    }
    memcpy(dup, sourceRange->first, lenInBytes);
    destRange->first = dup;
    destRange->afterLast = dup + lenInChars;

    return URI_TRUE;
}

UriBool URI_FUNC(CopyRangeAsNeeded)(URI_TYPE(TextRange) * destRange,
                                    const URI_TYPE(TextRange) * sourceRange,
                                    UriMemoryManager * memory) {
    if (sourceRange->first == NULL) {
        destRange->first = NULL;
        destRange->afterLast = NULL;
    } else if (sourceRange->first == sourceRange->afterLast) {
        destRange->first = URI_FUNC(SafeToPointTo);
        destRange->afterLast = URI_FUNC(SafeToPointTo);
    } else {
        return URI_FUNC(CopyRange)(destRange, sourceRange, memory);
    }

    return URI_TRUE;
}

UriBool URI_FUNC(RemoveDotSegmentsEx)(URI_TYPE(Uri) * uri, UriBool relative,
                                      UriBool pathOwned, UriMemoryManager * memory) {
    URI_TYPE(PathSegment) * walker;
    if ((uri == NULL) || (uri->pathHead == NULL)) {
        return URI_TRUE;
    }

    walker = uri->pathHead;
    walker->reserved = NULL; /* Prev pointer */
    do {
        UriBool removeSegment = URI_FALSE;
        int len = (int)(walker->text.afterLast - walker->text.first);
        switch (len) {
        case 1:
            if ((walker->text.first)[0] == _UT('.')) {
                /* "." segment -> remove if not essential */
                URI_TYPE(PathSegment) * const prev = walker->reserved;
                URI_TYPE(PathSegment) * const nextBackup = walker->next;

                /*
                 * Is this dot segment essential,
                 * i.e. is there a chance of changing semantics by dropping this dot
                 * segment?
                 *
                 * For example, changing "./http://foo" into "http://foo" would change
                 * semantics and hence the dot segment is essential to that case and
                 * cannot be removed.
                 *
                 * Other examples that would change semantics are:
                 * - cutting "/.//" down to "//"
                 * - cutting "scheme:/.//" down to "scheme://".
                 */
                removeSegment = URI_TRUE;
                if ((walker == uri->pathHead) && (walker->next != NULL)) {
                    /* Detect case "/.//" (with or without scheme) */
                    if ((walker->next->text.first == walker->next->text.afterLast)
                        && (URI_FUNC(HasHost)(uri) == URI_FALSE)) {
                        removeSegment = URI_FALSE;
                        /* Detect case "./withcolon:" */
                    } else if (relative) {
                        const URI_CHAR * ch = walker->next->text.first;
                        for (; ch < walker->next->text.afterLast; ch++) {
                            if (*ch == _UT(':')) {
                                removeSegment = URI_FALSE;
                                break;
                            }
                        }
                    }
                }

                if (removeSegment) {
                    /* .. then let's go remove that segment. */
                    /* Last segment? */
                    if (walker->next != NULL) {
                        /* Not last segment, i.e. first or middle segment
                         * OLD: (prev|NULL) <- walker <- next
                         * NEW: (prev|NULL) <----------- next */
                        walker->next->reserved = prev;

                        if (prev == NULL) {
                            /* First but not last segment
                             * OLD: head -> walker -> next
                             * NEW: head -----------> next */
                            uri->pathHead = walker->next;
                        } else {
                            /* Middle segment
                             * OLD: prev -> walker -> next
                             * NEW: prev -----------> next */
                            prev->next = walker->next;
                        }

                        if (pathOwned && (walker->text.first != walker->text.afterLast)) {
                            memory->free(memory, (URI_CHAR *)walker->text.first);
                        }
                        memory->free(memory, walker);
                    } else {
                        /* Last segment */
                        if (pathOwned && (walker->text.first != walker->text.afterLast)) {
                            memory->free(memory, (URI_CHAR *)walker->text.first);
                        }

                        if (prev == NULL) {
                            /* Last and first */
                            if (URI_FUNC(HasHost)(uri)) {
                                /* Replace "." with empty segment to represent trailing
                                 * slash */
                                walker->text.first = URI_FUNC(SafeToPointTo);
                                walker->text.afterLast = URI_FUNC(SafeToPointTo);
                            } else {
                                memory->free(memory, walker);

                                uri->pathHead = NULL;
                                uri->pathTail = NULL;
                            }
                        } else {
                            /* Last but not first, replace "." with empty segment to
                             * represent trailing slash */
                            walker->text.first = URI_FUNC(SafeToPointTo);
                            walker->text.afterLast = URI_FUNC(SafeToPointTo);
                        }
                    }

                    walker = nextBackup;
                }
            }
            break;

        case 2:
            if (((walker->text.first)[0] == _UT('.'))
                && ((walker->text.first)[1] == _UT('.'))) {
                /* Path ".." -> remove this and the previous segment */
                URI_TYPE(PathSegment) * const prev = walker->reserved;
                URI_TYPE(PathSegment) * prevPrev;
                URI_TYPE(PathSegment) * const nextBackup = walker->next;

                removeSegment = URI_TRUE;
                if (relative) {
                    if (prev == NULL) {
                        /* We cannot remove traversal beyond because the
                         * URI is relative and may be resolved later.
                         * So we can simplify "a/../b/d" to "b/d" but
                         * we cannot simplify "../b/d" (outside of reference resolution).
                         */
                        removeSegment = URI_FALSE;
                    } else if ((prev != NULL)
                               && ((prev->text.afterLast - prev->text.first) == 2)
                               && ((prev->text.first)[0] == _UT('.'))
                               && ((prev->text.first)[1] == _UT('.'))) {
                        /* We need to protect against mis-simplifying "a/../../b" to
                         * "a/b". */
                        removeSegment = URI_FALSE;
                    }
                }

                if (removeSegment) {
                    if (prev != NULL) {
                        /* Not first segment */
                        prevPrev = prev->reserved;
                        if (prevPrev != NULL) {
                            /* Not even prev is the first one
                             * OLD: prevPrev -> prev -> walker -> (next|NULL)
                             * NEW: prevPrev -------------------> (next|NULL) */
                            prevPrev->next = walker->next;
                            if (walker->next != NULL) {
                                /* Update parent relationship as well
                                 * OLD: prevPrev <- prev <- walker <- next
                                 * NEW: prevPrev <------------------- next */
                                walker->next->reserved = prevPrev;
                            } else {
                                /* Last segment -> insert "" segment to represent trailing
                                 * slash, update tail */
                                URI_TYPE(PathSegment) * const segment = memory->calloc(
                                    memory, 1, sizeof(URI_TYPE(PathSegment)));
                                if (segment == NULL) {
                                    if (pathOwned
                                        && (walker->text.first
                                            != walker->text.afterLast)) {
                                        memory->free(memory,
                                                     (URI_CHAR *)walker->text.first);
                                    }
                                    memory->free(memory, walker);

                                    if (pathOwned
                                        && (prev->text.first != prev->text.afterLast)) {
                                        memory->free(memory,
                                                     (URI_CHAR *)prev->text.first);
                                    }
                                    memory->free(memory, prev);

                                    return URI_FALSE; /* Raises malloc error */
                                }
                                segment->text.first = URI_FUNC(SafeToPointTo);
                                segment->text.afterLast = URI_FUNC(SafeToPointTo);
                                prevPrev->next = segment;
                                uri->pathTail = segment;
                            }

                            if (pathOwned
                                && (walker->text.first != walker->text.afterLast)) {
                                memory->free(memory, (URI_CHAR *)walker->text.first);
                            }
                            memory->free(memory, walker);

                            if (pathOwned && (prev->text.first != prev->text.afterLast)) {
                                memory->free(memory, (URI_CHAR *)prev->text.first);
                            }
                            memory->free(memory, prev);

                            walker = nextBackup;
                        } else {
                            /* Prev is the first segment */
                            if (walker->next != NULL) {
                                uri->pathHead = walker->next;
                                walker->next->reserved = NULL;

                                if (pathOwned
                                    && (walker->text.first != walker->text.afterLast)) {
                                    memory->free(memory, (URI_CHAR *)walker->text.first);
                                }
                                memory->free(memory, walker);
                            } else {
                                /* Reuse segment for "" path segment to represent trailing
                                 * slash, update tail */
                                URI_TYPE(PathSegment) * const segment = walker;
                                if (pathOwned
                                    && (segment->text.first != segment->text.afterLast)) {
                                    memory->free(memory, (URI_CHAR *)segment->text.first);
                                }
                                segment->text.first = URI_FUNC(SafeToPointTo);
                                segment->text.afterLast = URI_FUNC(SafeToPointTo);
                                uri->pathHead = segment;
                                uri->pathTail = segment;
                            }

                            if (pathOwned && (prev->text.first != prev->text.afterLast)) {
                                memory->free(memory, (URI_CHAR *)prev->text.first);
                            }
                            memory->free(memory, prev);

                            walker = nextBackup;
                        }
                    } else {
                        URI_TYPE(PathSegment) * const anotherNextBackup = walker->next;
                        int freeWalker = URI_TRUE;

                        /* First segment */
                        if (walker->next != NULL) {
                            /* First segment of multiple -> update head
                             * OLD: head -> walker -> next
                             * NEW: head -----------> next */
                            uri->pathHead = walker->next;

                            /* Update parent link as well
                             * OLD: head <- walker <- next
                             * NEW: head <----------- next */
                            walker->next->reserved = NULL;
                        } else {
                            if (uri->absolutePath) {
                                /* First and only segment -> update head
                                 * OLD: head -> walker -> NULL
                                 * NEW: head -----------> NULL */
                                uri->pathHead = NULL;

                                /* Last segment -> update tail
                                 * OLD: tail -> walker
                                 * NEW: tail -> NULL */
                                uri->pathTail = NULL;
                            } else {
                                /* Reuse segment for "" path segment to represent trailing
                                 * slash, then update head and tail */
                                if (pathOwned
                                    && (walker->text.first != walker->text.afterLast)) {
                                    memory->free(memory, (URI_CHAR *)walker->text.first);
                                }
                                walker->text.first = URI_FUNC(SafeToPointTo);
                                walker->text.afterLast = URI_FUNC(SafeToPointTo);
                                freeWalker = URI_FALSE;
                            }
                        }

                        if (freeWalker) {
                            if (pathOwned
                                && (walker->text.first != walker->text.afterLast)) {
                                memory->free(memory, (URI_CHAR *)walker->text.first);
                            }
                            memory->free(memory, walker);
                        }

                        walker = anotherNextBackup;
                    }
                }
            }
            break;
        } /* end of switch */

        if (!removeSegment) {
            /* .. then let's move to the next element, and start again. */
            if (walker->next != NULL) {
                walker->next->reserved = walker;
            } else {
                /* Last segment -> update tail */
                uri->pathTail = walker;
            }
            walker = walker->next;
        }
    } while (walker != NULL);

    return URI_TRUE;
}

/* Properly removes "." and ".." path segments */
UriBool URI_FUNC(RemoveDotSegmentsAbsolute)(URI_TYPE(Uri) * uri,
                                            UriMemoryManager * memory) {
    const UriBool ABSOLUTE = URI_FALSE;
    if (uri == NULL) {
        return URI_TRUE;
    }
    return URI_FUNC(RemoveDotSegmentsEx)(uri, ABSOLUTE, uri->owner, memory);
}

unsigned char URI_FUNC(HexdigToInt)(URI_CHAR hexdig) {
    switch (hexdig) {
    case URI_SET_DIGIT(_UT):
        return (unsigned char)(9 + hexdig - _UT('9'));
    case URI_SET_HEX_LETTER_LOWER(_UT):
        return (unsigned char)(15 + hexdig - _UT('f'));
    case URI_SET_HEX_LETTER_UPPER(_UT):
        return (unsigned char)(15 + hexdig - _UT('F'));

    default:
        return 0;
    }
}

URI_CHAR URI_FUNC(HexToLetterEx)(unsigned int value, UriBool uppercase) {
    switch (value) {
    case 0:
        return _UT('0');
    case 1:
        return _UT('1');
    case 2:
        return _UT('2');
    case 3:
        return _UT('3');
    case 4:
        return _UT('4');
    case 5:
        return _UT('5');
    case 6:
        return _UT('6');
    case 7:
        return _UT('7');
    case 8:
        return _UT('8');
    case 9:
        return _UT('9');

    case 10:
        return (uppercase == URI_TRUE) ? _UT('A') : _UT('a');
    case 11:
        return (uppercase == URI_TRUE) ? _UT('B') : _UT('b');
    case 12:
        return (uppercase == URI_TRUE) ? _UT('C') : _UT('c');
    case 13:
        return (uppercase == URI_TRUE) ? _UT('D') : _UT('d');
    case 14:
        return (uppercase == URI_TRUE) ? _UT('E') : _UT('e');
    default:
        return (uppercase == URI_TRUE) ? _UT('F') : _UT('f');
    }
}

/* Checks if a URI has the host component set. */
UriBool URI_FUNC(HasHost)(const URI_TYPE(Uri) * uri) {
    /* NOTE: .hostData.ipFuture.first is not being checked,   *
     *       because we do check .hostText.first and          *
     *       .hostData.ipFuture.first has to be identical to  *
     *       .hostText.first if set, and hence there is       *
     *       no more information to be gained.                */
    return (uri != NULL)
           && ((uri->hostText.first != NULL) || (uri->hostData.ip4 != NULL)
               || (uri->hostData.ip6 != NULL));
}

/* Copies the path segment list from one URI to another. */
UriBool URI_FUNC(CopyPath)(URI_TYPE(Uri) * dest, const URI_TYPE(Uri) * source,
                           UriMemoryManager * memory) {
    if (source->pathHead == NULL) {
        /* No path component */
        dest->pathHead = NULL;
        dest->pathTail = NULL;
    } else {
        /* Copy list but not the text contained */
        URI_TYPE(PathSegment) * sourceWalker = source->pathHead;
        URI_TYPE(PathSegment) * destPrev = NULL;
        do {
            URI_TYPE(PathSegment) * cur =
                memory->malloc(memory, sizeof(URI_TYPE(PathSegment)));
            if (cur == NULL) {
                /* Fix broken list */
                if (destPrev != NULL) {
                    destPrev->next = NULL;
                }
                return URI_FALSE; /* Raises malloc error */
            }

            /* From this functions usage we know that *
             * the dest URI cannot be uri->owner      */
            cur->text = sourceWalker->text;
            if (destPrev == NULL) {
                /* First segment ever */
                dest->pathHead = cur;
            } else {
                destPrev->next = cur;
            }
            destPrev = cur;
            sourceWalker = sourceWalker->next;
        } while (sourceWalker != NULL);
        dest->pathTail = destPrev;
        dest->pathTail->next = NULL;
    }

    dest->absolutePath = source->absolutePath;
    return URI_TRUE;
}

/* Copies the authority part of an URI over to another. */
UriBool URI_FUNC(CopyAuthority)(URI_TYPE(Uri) * dest, const URI_TYPE(Uri) * source,
                                UriMemoryManager * memory) {
    /* From this functions usage we know that *
     * the dest URI cannot be uri->owner      */

    /* Copy userInfo */
    dest->userInfo = source->userInfo;

    /* Copy hostText */
    dest->hostText = source->hostText;

    /* Copy hostData */
    if (source->hostData.ip4 != NULL) {
        dest->hostData.ip4 = memory->malloc(memory, sizeof(UriIp4));
        if (dest->hostData.ip4 == NULL) {
            return URI_FALSE; /* Raises malloc error */
        }
        *(dest->hostData.ip4) = *(source->hostData.ip4);
        dest->hostData.ip6 = NULL;
        dest->hostData.ipFuture.first = NULL;
        dest->hostData.ipFuture.afterLast = NULL;
    } else if (source->hostData.ip6 != NULL) {
        dest->hostData.ip4 = NULL;
        dest->hostData.ip6 = memory->malloc(memory, sizeof(UriIp6));
        if (dest->hostData.ip6 == NULL) {
            return URI_FALSE; /* Raises malloc error */
        }
        *(dest->hostData.ip6) = *(source->hostData.ip6);
        dest->hostData.ipFuture.first = NULL;
        dest->hostData.ipFuture.afterLast = NULL;
    } else {
        dest->hostData.ip4 = NULL;
        dest->hostData.ip6 = NULL;
        dest->hostData.ipFuture = source->hostData.ipFuture;
    }

    /* Copy portText */
    dest->portText = source->portText;

    return URI_TRUE;
}

UriBool URI_FUNC(FixAmbiguity)(URI_TYPE(Uri) * uri, UriMemoryManager * memory) {
    URI_TYPE(PathSegment) * segment;

    if (/* Case 1: absolute path, empty first segment */
        (uri->absolutePath && (uri->pathHead != NULL)
         && (uri->pathHead->text.afterLast == uri->pathHead->text.first))

        /* Case 2: relative path, empty first and second segment */
        || (!uri->absolutePath && (uri->pathHead != NULL) && (uri->pathHead->next != NULL)
            && (uri->pathHead->text.afterLast == uri->pathHead->text.first)
            && (uri->pathHead->next->text.afterLast
                == uri->pathHead->next->text.first))) {
        /* NOOP */
    } else {
        return URI_TRUE;
    }

    segment = memory->malloc(memory, 1 * sizeof(URI_TYPE(PathSegment)));
    if (segment == NULL) {
        return URI_FALSE; /* Raises malloc error */
    }

    /* Insert "." segment in front */
    segment->next = uri->pathHead;
    segment->text.first = URI_FUNC(ConstPwd);
    segment->text.afterLast = URI_FUNC(ConstPwd) + 1;
    uri->pathHead = segment;
    return URI_TRUE;
}

static UriBool URI_FUNC(PrependNewDotSegment)(URI_TYPE(Uri) * uri,
                                              UriMemoryManager * memory) {
    assert(uri != NULL);
    assert(memory != NULL);

    URI_TYPE(PathSegment) * const segment =
        memory->malloc(memory, 1 * sizeof(URI_TYPE(PathSegment)));

    if (segment == NULL) {
        return URI_FALSE; /* i.e. raise malloc error */
    }

    segment->next = uri->pathHead;

    URI_TYPE(TextRange) dotRange;
    dotRange.first = URI_FUNC(ConstPwd);
    dotRange.afterLast = URI_FUNC(ConstPwd) + 1;

    if (uri->owner == URI_TRUE) {
        if (URI_FUNC(CopyRange)(&(segment->text), &dotRange, memory) == URI_FALSE) {
            memory->free(memory, segment);
            return URI_FALSE; /* i.e. raise malloc error */
        }
    } else {
        segment->text = dotRange; /* copies all members */
    }

    uri->pathHead = segment;

    return URI_TRUE;
}

/* When dropping a scheme from a URI without a host and with a colon (":")
 * in the first path segment, a consecutive reparse would rightfully
 * mis-classify the first path segment as a scheme due to the colon.
 * To protect against this case, we prepend an artificial "." segment
 * to the path in here; the function is called after the scheme has
 * just been dropped.
 *
 * 0. We start with parsed URI "scheme:path1:/path2/path3".
 * 1. We drop the scheme naively and yield "path1:/path2/path3".
 * 2. We prepend "." and yield unambiguous "./path1:/path2/path3".
 *
 * From the view of the RFC 3986 grammar, this is replacing rule path-rootless
 * by path-noscheme content.
 *
 * Returns URI_TRUE for (a) nothing to do or (b) successful changes.
 * Returns URI_FALSE to signal out-of-memory.
 */
UriBool URI_FUNC(FixPathNoScheme)(URI_TYPE(Uri) * uri, UriMemoryManager * memory) {
    assert(uri != NULL);
    assert(memory != NULL);

    if ((uri->absolutePath == URI_TRUE) || (uri->pathHead == NULL)
        || (uri->scheme.first != NULL) || URI_FUNC(HasHost)(uri)) {
        return URI_TRUE; /* i.e. nothing to do */
    }

    /* Check for troublesome first path segment containing a colon */
    UriBool colonFound = URI_FALSE;
    const URI_CHAR * walker = uri->pathHead->text.first;

    while (walker < uri->pathHead->text.afterLast) {
        if (walker[0] == _UT(':')) {
            colonFound = URI_TRUE;
            break;
        }
        walker++;
    }

    assert((walker == uri->pathHead->text.afterLast) || (colonFound == URI_TRUE));

    if (colonFound == URI_FALSE) {
        return URI_TRUE; /* i.e. nothing to do */
    }

    /* Insert "." segment in front */
    return URI_FUNC(PrependNewDotSegment)(uri, memory);
}

/* When dropping a host from a URI without a scheme, an absolute path
 * and empty first path segment, a consecutive reparse would rightfully
 * mis-classify the first path segment as a host marker due to the "//".
 * To protect against this case, we prepend an artificial "." segment
 * to the path in here; the function is called after the host has
 * just been dropped.
 *
 * 0. We start with parsed URI "//host//path1/path2".
 * 1. We drop the host naively and yield "//path1/path2".
 * 2. We insert "./" and yield unambiguous "/.//path1/path2".
 *
 * Returns URI_TRUE for (a) nothing to do or (b) successful changes.
 * Returns URI_FALSE to signal out-of-memory.
 */
UriBool URI_FUNC(EnsureThatPathIsNotMistakenForHost)(URI_TYPE(Uri) * uri,
                                                     UriMemoryManager * memory) {
    assert(uri != NULL);
    assert(memory != NULL);

    if ((URI_FUNC(HasHost)(uri) == URI_TRUE) || (uri->absolutePath == URI_FALSE)
        || (uri->pathHead == NULL)
        || (uri->pathHead == uri->pathTail) /* i.e. no second slash */
        || (uri->pathHead->text.first != uri->pathHead->text.afterLast)) {
        return URI_TRUE; /* i.e. nothing to do */
    }

    /* Insert "." segment in front */
    return URI_FUNC(PrependNewDotSegment)(uri, memory);
}

void URI_FUNC(FixEmptyTrailSegment)(URI_TYPE(Uri) * uri, UriMemoryManager * memory) {
    /* Fix path if only one empty segment */
    if (!uri->absolutePath && !URI_FUNC(HasHost)(uri) && (uri->pathHead != NULL)
        && (uri->pathHead->next == NULL)
        && (uri->pathHead->text.first == uri->pathHead->text.afterLast)) {
        memory->free(memory, uri->pathHead);
        uri->pathHead = NULL;
        uri->pathTail = NULL;
    }
}

#endif