if (SG(post_max_size) > 0 && SG(request_info).content_length > SG(post_max_size)) {
    sapi_module.sapi_error(E_WARNING, "POST Content-Length of " ZEND_LONG_FMT " bytes exceeds the limit of " ZEND_LONG_FMT " bytes", SG(request_info).content_length, SG(post_max_size));
    return;
}

/* Get the boundary */
boundary = strstr(content_type_dup, "boundary");//查找是否包含boundary
if (!boundary) {
    int content_type_len = (int)strlen(content_type_dup);
    char *content_type_lcase = estrndup(content_type_dup, content_type_len);
    
    php_strtolower(content_type_lcase, content_type_len);
    boundary = strstr(content_type_lcase, "boundary");
    if (boundary) {
        boundary = content_type_dup + (boundary - content_type_lcase);
    }
    efree(content_type_lcase);
}

if (!boundary || !(boundary = strchr(boundary, '='))) {//判断boundary值起始位置
    sapi_module.sapi_error(E_WARNING, "Missing boundary in multipart/form-data POST data");
    return;//传入畸形的boundary会抛出警告 (可以用来检测目标php是否开启错误回显)
}

boundary++;
boundary_len = (int)strlen(boundary);

if (boundary[0] == '"') {//引号包裹
    boundary++;
    boundary_end = strchr(boundary, '"');
    if (!boundary_end) {
        sapi_module.sapi_error(E_WARNING, "Invalid boundary in multipart/form-data POST data");
        return;
    }
} else {//非引号包裹
    /* search for the end of the boundary */
    boundary_end = strpbrk(boundary, ",;");//截止字符
}
if (boundary_end) {
    boundary_end[0] = '\0';
    boundary_len = boundary_end-boundary;
}

/* Initialize the buffer */
if (!(mbuff = multipart_buffer_new(boundary, boundary_len))) {
    sapi_module.sapi_error(E_WARNING, "Unable to initialize the input buffer");
    return;
	}

static multipart_buffer *multipart_buffer_new(char *boundary, int boundary_len)
{
    multipart_buffer *self = (multipart_buffer *) ecalloc(1, sizeof(multipart_buffer));
    
    int minsize = boundary_len + 6;
    if (minsize < FILLUNIT) minsize = FILLUNIT;
    
    self->buffer = (char *) ecalloc(1, minsize + 1);
    self->bufsize = minsize;
    
    spprintf(&self->boundary, 0, "--%s", boundary);
    
    self->boundary_next_len = (int)spprintf(&self->boundary_next, 0, "\n--%s", boundary);
    
    self->buf_begin = self->buffer;
    self->bytes_in_buffer = 0;
    
    if (php_rfc1867_encoding_translation()) {
        php_rfc1867_get_detect_order(&self->detect_order, &self->detect_order_size);
    } else {
        self->detect_order = NULL;
        self->detect_order_size = 0;
    }
    
    self->input_encoding = NULL;
    
    return self;
}

if (!multipart_buffer_headers(mbuff, &header)) { //获取multipart头
	goto fileupload_done;
}
if ((cd = php_mime_get_hdr_value(header, "Content-Disposition"))) {
	char *pair = NULL;
	int end = 0;
	while (isspace(*cd)) {
		++cd;
	}
	while (*cd && (pair = getword(mbuff->input_encoding, &cd, ';'))) {
		char *key = NULL, *word = pair;
		while (isspace(*cd)) {
			++cd;
		}
		if (strchr(pair, '=')) {
			key = getword(mbuff->input_encoding, &pair, '=');
			if (!strcasecmp(key, "name")) {
				if (param) {
					efree(param);
				}
				param = getword_conf(mbuff->input_encoding, pair);
				if (mbuff->input_encoding && internal_encoding) {
					unsigned char *new_param;
					size_t new_param_len;
					if ((size_t)-1 != zend_multibyte_encoding_converter(&new_param, &new_param_len, (unsigned char *)param, strlen(param), internal_encoding, mbuff->input_encoding)) {
						efree(param);
						param = (char *)new_param;
					}
				}
			} else if (!strcasecmp(key, "filename")) {
				if (filename) {
					efree(filename);
				}
				filename = getword_conf(mbuff->input_encoding, pair);
				if (mbuff->input_encoding && internal_encoding) {
					unsigned char *new_filename;
					size_t new_filename_len;
					if ((size_t)-1 != zend_multibyte_encoding_converter(&new_filename, &new_filename_len, (unsigned char *)filename, strlen(filename), internal_encoding, mbuff->input_encoding)) {
						efree(filename);
						filename = (char *)new_filename;
					}
				}
			}
		}
		if (key) {
			efree(key);
		}
		efree(word);
	}

static int multipart_buffer_headers(multipart_buffer *self, zend_llist *header)
{
	char *line;
	mime_header_entry entry = {0};
	smart_string buf_value = {0};
	char *key = NULL;

	/* didn't find boundary, abort */
	if (!find_boundary(self, self->boundary)) {//匹配分界线
		return 0;
	}

	/* get lines of text, or CRLF_CRLF */

	while ((line = get_line(self)) && line[0] != '\0') {//获取下一行字符串 [1]
		/* add header to table */
		char *value = NULL;

		if (php_rfc1867_encoding_translation()) { //[2] 判断编码 之后处理字符串会用到 好像默认禁用 写死了返回0??
			self->input_encoding = zend_multibyte_encoding_detector((const unsigned char *) line, strlen(line), self->detect_order, self->detect_order_size);
		}

		/* space in the beginning means same header */
		if (!isspace(line[0])) {
			value = strchr(line, ':');
		}

		if (value) {
			if (buf_value.c && key) {
				/* new entry, add the old one to the list */
				smart_string_0(&buf_value);
				entry.key = key;
				entry.value = buf_value.c;
				zend_llist_add_element(header, &entry);
				buf_value.c = NULL;
				key = NULL;
			}

			*value = '\0';
			do { value++; } while (isspace(*value));

			key = estrdup(line);
			smart_string_appends(&buf_value, value);
		} else if (buf_value.c) { /* If no ':' on the line, add to previous line */
			smart_string_appends(&buf_value, line);  //[2]  如果没有冒号就作为上一行的值
		} else {
			continue;
		}
	}

	if (buf_value.c && key) {
		/* add the last one to the list */
		smart_string_0(&buf_value);
		entry.key = key;
		entry.value = buf_value.c;
		zend_llist_add_element(header, &entry);
	}

	return 1;
}

static char *get_line(multipart_buffer *self)
{
	char* ptr = next_line(self);

	if (!ptr) {
		fill_buffer(self);
		ptr = next_line(self);
	}

	return ptr;
}

/* The \ check should technically be needed for win32 systems only where
* it is a valid path separator. However, IE in all it's wisdom always sends
* the full path of the file on the user's filesystem, which means that unless
* the user does basename() they get a bogus file name. Until IE's user base drops
* to nill or problem is fixed this code must remain enabled for all systems. */
s = _basename(internal_encoding, filename);
if (!s) {
s = filename;
}

PHPAPI zend_string *php_basename(const char *s, size_t len, char *suffix, size_t sufflen)
{
	char *c;
	const char *comp, *cend;
	size_t inc_len, cnt;
	int state;
	zend_string *ret;

	comp = cend = c = (char*)s;
	cnt = len;
	state = 0;
	while (cnt > 0) {
		inc_len = (*c == '\0' ? 1 : php_mblen(c, cnt));

		switch (inc_len) {
			case -2:
			case -1:
				inc_len = 1;
				php_mb_reset();
				break;
			case 0:
				goto quit_loop;
			case 1:
#if defined(PHP_WIN32)
				if (*c == '/' || *c == '\\') {
#else
				if (*c == '/') {
#endif
					if (state == 1) {
						state = 0;
						cend = c;
					}
#if defined(PHP_WIN32)
				/* Catch relative paths in c:file.txt style. They're not to confuse
				   with the NTFS streams. This part ensures also, that no drive
				   letter traversing happens. */
				} else if ((*c == ':' && (c - comp == 1))) {
					if (state == 0) {
						comp = c;
						state = 1;
					} else {
						cend = c;
						state = 0;
					}
#endif
				} else {
					if (state == 0) {
						comp = c;
						state = 1;
					}
				}
				break;
			default:
				if (state == 0) {
					comp = c;
					state = 1;
				}
				break;
		}
		c += inc_len;
		cnt -= inc_len;
	}

quit_loop:
	if (state == 1) {
		cend = c;
	}
	if (suffix != NULL && sufflen < (size_t)(cend - comp) &&
			memcmp(cend - sufflen, suffix, sufflen) == 0) {
		cend -= sufflen;
	}

	len = cend - comp;

	ret = zend_string_init(comp, len, 0);
	return ret;
}