typedef some recurring function signatures

2 files changed, 38 insertions, 9 deletions

diff --git a/src/pj_init.c b/src/pj_init.c
index f54a2a92..3c36fc3a 100644
--- a/src/pj_init.c
+++ b/src/pj_init.c
@@ -470,22 +470,20 @@ pj_init(int argc, char **argv) {
 }
 
 
-typedef    PJ *(constructor)(PJ *);
-
-static constructor *pj_constructor (const char *name) {
+static PJ_CONSTRUCTOR pj_locate_constructor (const char *name) {
     int i;
     char *s;
     for (i = 0; (s = pj_list[i].id) && strcmp(name, s) ; ++i) ;
     if (0==s)
         return 0;
-    return (constructor *) pj_list[i].proj;
+    return (PJ_CONSTRUCTOR) pj_list[i].proj;
 }
 
 
 PJ *
 pj_init_ctx(projCtx ctx, int argc, char **argv) {
     char *s, *name;
-    constructor *proj;
+    PJ_CONSTRUCTOR proj;
     paralist *curr, *init, *start;
     int i;
     int err;
@@ -559,7 +557,7 @@ pj_init_ctx(projCtx ctx, int argc, char **argv) {
         return pj_dealloc_params (ctx, start, PJD_ERR_PROJ_NOT_NAMED);
     name += 5;
 
-    proj = pj_constructor (name);
+    proj = pj_locate_constructor (name);
     if (0==proj)
         return pj_dealloc_params (ctx, start, PJD_ERR_UNKNOWN_PROJECTION_ID);
 
diff --git a/src/projects.h b/src/projects.h
index bfbe08cb..25ff82a4 100644
--- a/src/projects.h
+++ b/src/projects.h
@@ -218,6 +218,37 @@ struct PJ_AREA {
 struct projCtx_t;
 typedef struct projCtx_t projCtx_t;
 
+/*****************************************************************************
+
+    Some function types that are especially useful when working with PJs
+
+******************************************************************************
+
+PJ_CONSTRUCTOR:
+
+    A function taking a pointer-to-PJ as arg, and returning a pointer-to-PJ.
+    Historically called twice: First with a 0 argument, to allocate memory,
+    second with the first return value as argument, for actual setup.
+
+PJ_DESTRUCTOR:
+
+    A function taking a pointer-to-PJ and an integer as args, then first
+    handling the deallocation of the PJ, afterwards handing the integer over
+    to the error reporting subsystem, and finally returning a null pointer in
+    support of the "return free (P)" (aka "get the hell out of here") idiom.
+
+PJ_OPERATOR:
+
+    A function taking a PJ_COORD and a pointer-to-PJ as args, applying the
+    PJ to the PJ_COORD, and returning the resulting PJ_COORD.
+
+*****************************************************************************/
+typedef    PJ       *(* PJ_CONSTRUCTOR) (PJ *);
+typedef    void     *(* PJ_DESTRUCTOR)  (PJ *, int);
+typedef    PJ_COORD  (* PJ_OPERATOR)    (PJ_COORD, PJ *);
+/****************************************************************************/
+
+
 
 /* base projection data structure */
 struct PJconsts {
@@ -267,10 +298,10 @@ struct PJconsts {
     LP  (*inv)(XY,    PJ *);
     XYZ (*fwd3d)(LPZ, PJ *);
     LPZ (*inv3d)(XYZ, PJ *);
-    PJ_COORD (*fwd4d)(PJ_COORD, PJ *);
-    PJ_COORD (*inv4d)(PJ_COORD, PJ *);
+    PJ_OPERATOR fwd4d;
+    PJ_OPERATOR inv4d;
 
-    void *(*destructor)(PJ *, int);
+    PJ_DESTRUCTOR destructor;
 
 
     /*************************************************************************************