Pipeline and cct inverse fixes

src/PJ_pipeline.c

@@ -429,14 +429,42 @@ PJ *OPERATION(pipeline,0) {
 
         /* Is this step inverted? */
         for (j = 0;  j < current_argc; j++)
-            if (0==strcmp("inv", current_argv[j]))
-                next_step->inverted = 1;
+            if (0==strcmp("inv", current_argv[j])) {
+                /* if +inv exists in both global and local args the forward operation should be used */
+                next_step->inverted = next_step->inverted == 0 ? 1 : 0;
+            }
 
         P->opaque->pipeline[i+1] = next_step;
 
         proj_log_trace (P, "Pipeline at [%p]:    step at [%p] done", P, next_step);
     }
 
+    /* Require a forward path through the pipeline */
+    for (i = 1; i <= nsteps; i++) {
+        PJ *Q = P->opaque->pipeline[i];
+        if ( ( Q->inverted && (Q->inv || Q->inv3d || Q->fwd4d) ) ||
+             (!Q->inverted && (Q->fwd || Q->fwd3d || Q->fwd4d) ) ) {
+            continue;
+        } else {
+            proj_log_error (P, "Pipeline: A forward operation couldn't be constructed");
+            return destructor (P, PJD_ERR_MALFORMED_PIPELINE);
+        }
+    }
+
+    /* determine if an inverse operation is possible */
+    for (i = 1; i <= nsteps; i++) {
+        PJ *Q = P->opaque->pipeline[i];
+        if ( ( Q->inverted && (Q->fwd || Q->fwd3d || Q->fwd4d) ) ||
+             ( Q->inv || Q->inv3d || Q->inv4d) ) {
+            continue;
+        } else {
+            P->inv   = 0;
+            P->inv3d = 0;
+            P->inv4d = 0;
+            break;
+        }
+    }
+
     proj_log_trace (P, "Pipeline: %d steps built. Determining i/o characteristics", nsteps);
 
     /* Determine forward input (= reverse output) data type */

src/cct.c

@@ -217,9 +217,15 @@ int main(int argc, char **argv) {
         return 1;
     }
 
-    /* We have no API call for inverting an operation, so we brute force it. */
-    if (direction==-1)
+    if (direction==-1) {
+        /* fail if an inverse operation is not available */
+        if (!proj_pj_info(P).has_inverse) {
+            fprintf (stderr, "Inverse operation not available\n");
+            return 1;
+        }
+        /* We have no API call for inverting an operation, so we brute force it. */
         P->inverted = !(P->inverted);
+    }
     direction = 1;
 
     /* Allocate input buffer */

test/gie/more_builtins.gie

@@ -65,7 +65,7 @@ roundtrip 100    1 m
 -------------------------------------------------------------------------------
 Some tests from PJ_pipeline.c
 -------------------------------------------------------------------------------
-Forward-reverse geo->utm->geo
+Forward-reverse geo->utm->geo (4D functions)
 -------------------------------------------------------------------------------
 operation proj=pipeline zone=32 step
           proj=utm  ellps=GRS80 step
@@ -81,7 +81,7 @@ Now the inverse direction (still same result: the pipeline is symmetrical)
 direction inverse
 expect 12 55 0 0
 -------------------------------------------------------------------------------
-And now the back-to-back situation utm->geo->utm
+And now the back-to-back situation utm->geo->utm (4D functions)
 -------------------------------------------------------------------------------
 operation proj=pipeline zone=32 ellps=GRS80 step
           proj=utm inv                      step
@@ -92,6 +92,33 @@ expect 691875.63214  6098907.82501  0  0
 direction inverse
 expect 691875.63214  6098907.82501  0  0
 -------------------------------------------------------------------------------
+Forward-reverse geo->utm->geo (3D functions)
+-------------------------------------------------------------------------------
+operation proj=pipeline zone=32 step
+          proj=utm  ellps=GRS80 step
+          proj=utm  ellps=GRS80 inv
+-------------------------------------------------------------------------------
+tolerance 0.1 mm
+
+accept 12 55 0
+expect 12 55 0
+
+Now the inverse direction (still same result: the pipeline is symmetrical)
+
+direction inverse
+expect 12 55 0
+-------------------------------------------------------------------------------
+And now the back-to-back situation utm->geo->utm (3D functions)
+-------------------------------------------------------------------------------
+operation proj=pipeline zone=32 ellps=GRS80 step
+          proj=utm inv                      step
+          proj=utm
+-------------------------------------------------------------------------------
+accept 691875.63214  6098907.82501  0
+expect 691875.63214  6098907.82501  0
+direction inverse
+expect 691875.63214  6098907.82501  0
+-------------------------------------------------------------------------------
 Test a corner case: A rather pointless one-step pipeline geo->utm
 -------------------------------------------------------------------------------
 operation proj=pipeline step proj=utm zone=32 ellps=GRS80
@@ -115,9 +142,39 @@ expect    691875.63214  6098907.82501  0  0
 direction inverse
 accept    12 55 0 0
 expect    12 55 0 0
+-------------------------------------------------------------------------------
+Test a few inversion scenarios (urm5 has no inverse operation)
+-------------------------------------------------------------------------------
+operation   proj=pipeline       step
+            proj=urm5 n=0.5 inv
+expect      failure pjd_err_malformed_pipeline
+
+operation   proj=pipeline   inv step
+            proj=urm5 n=0.5
+expect      failure pjd_err_malformed_pipeline
 
+operation   proj=pipeline   inv step
+            proj=urm5 n=0.5 inv
+accept      12 56
+expect      1215663.2814182492      5452209.5424045017
+
+operation   proj=pipeline step
+            proj=urm5 n=0.5
+accept      12 56
+expect      1215663.2814182492      5452209.5424045017
+-------------------------------------------------------------------------------
+Test various failing scenarios.
+-------------------------------------------------------------------------------
+operation   proj=pipeline   step
+            proj=pipeline   step
+            proj=merc
+expect      failure pjd_err_malformed_pipeline
 
+operation   step proj=pipeline step proj=merc
+expect      failure pjd_err_malformed_pipeline
 
+operation   proj=pipeline
+expect      failure pjd_err_malformed_pipeline
 
 
 -------------------------------------------------------------------------------