Add: string_len_trim to check for empty source files (#335)

Fixes performance regression from 33ad2ce. Don't use string_cat for checking for empty source files.

Author: LKedward

fpm/src/fpm_source_parsing.f90

@@ -16,7 +16,7 @@
 !>
 module fpm_source_parsing
 use fpm_error, only: error_t, file_parse_error, fatal_error
-use fpm_strings, only: string_t, string_cat, split, lower, str_ends_with, fnv_1a
+use fpm_strings, only: string_t, string_cat, len_trim, split, lower, str_ends_with, fnv_1a
 use fpm_model, only: srcfile_t, &
                     FPM_UNIT_UNKNOWN, FPM_UNIT_PROGRAM, FPM_UNIT_MODULE, &
                     FPM_UNIT_SUBMODULE, FPM_UNIT_SUBPROGRAM, &
@@ -87,7 +87,7 @@ function parse_f_source(f_filename,error) result(f_source)
     close(fh)
 
     ! Ignore empty files, returned as FPM_UNIT_UNKNOW
-    if (len_trim(string_cat(file_lines,' ')) < 1) return
+    if (len_trim(file_lines) < 1) return
 
     f_source%digest = fnv_1a(file_lines)
 
@@ -392,7 +392,7 @@ function parse_c_source(c_filename,error) result(c_source)
     close(fh)
 
     ! Ignore empty files, returned as FPM_UNIT_UNKNOW
-    if (len_trim(string_cat(file_lines,' ')) < 1) then
+    if (len_trim(file_lines) < 1) then
         c_source%unit_type = FPM_UNIT_UNKNOWN
         return
     end if

fpm/src/fpm_strings.f90

@@ -4,13 +4,17 @@ module fpm_strings
 
 private
 public :: f_string, lower, split, str_ends_with, string_t
-public :: string_array_contains, string_cat, operator(.in.), fnv_1a
+public :: string_array_contains, string_cat, len_trim, operator(.in.), fnv_1a
 public :: resize, str
 
 type string_t
     character(len=:), allocatable :: s
 end type
 
+interface len_trim
+    module procedure :: string_len_trim
+end interface len_trim
+
 interface resize
   module procedure :: resize_string
 end interface
@@ -200,6 +204,19 @@ function string_cat(strings,delim) result(cat)
 
 end function string_cat
 
+
+!> Determine total trimmed length of `string_t` array
+pure function string_len_trim(strings) result(n)
+    type(string_t), intent(in) :: strings(:)
+    integer :: i, n
+
+    n = 0
+    do i=1,size(strings)
+        n = n + len_trim(strings(i)%s)
+    end do
+
+end function string_len_trim
+
 subroutine split(input_line,array,delimiters,order,nulls)
     ! parse string on delimiter characters and store tokens into an allocatable array"
     ! Author: John S. Urban