From 0cdb914b5764f692189ed2bc395e3b09ead758e4 Mon Sep 17 00:00:00 2001
From: Ian Jauslin <ian@jauslin.org>
Date: Fri, 27 May 2022 16:09:17 -0400
Subject: savefile and initfile

---
 src/io.c | 112 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 112 insertions(+)
 create mode 100644 src/io.c

(limited to 'src/io.c')

diff --git a/src/io.c b/src/io.c
new file mode 100644
index 0000000..5cdfc54
--- /dev/null
+++ b/src/io.c
@@ -0,0 +1,112 @@
+#include <stdbool.h>
+#include <stdlib.h>
+#include "io.h"
+#include "navier-stokes.h"
+
+// write final entry to file
+int write_u(_Complex double* u, int K1, int K2, FILE* file){
+  int kx,ky;
+
+  // do nothing if there is no file
+  if(file==NULL){
+    return 0;
+  }
+
+  for(kx=-K1;kx<=K1;kx++){
+    for (ky=-K2;ky<=K2;ky++){
+      fprintf(file,"%d %d % .15e % .15e\n",kx,ky,__real__ u[klookup(kx,ky,2*K1+1,2*K2+1)],__imag__ u[klookup(kx,ky,2*K1+1,2*K2+1)]);
+    }
+  }
+
+  return 0;
+}
+
+// read u from file
+int read_u(_Complex double* u, int K1, int K2, FILE* file){
+  int kx,ky;
+  double r,i;
+  char* line;
+  unsigned int len=256;
+  unsigned int pos=0;
+  char* line_realloc;
+  char c;
+  int ret;
+  unsigned int counter=0;
+  bool commented=false;
+
+  // error if there is no file (this should not happen)
+  if (file==NULL){
+    fprintf(stderr,"error reading u from file (this is a bug!)\n");
+    return -1;
+  }
+
+  // allocate line buffer
+  line=calloc(sizeof(char), len);
+
+  while(1){
+    c=fgetc(file);
+
+    // end of file
+    if (feof(file)){
+      break;
+    }
+
+    // newline: read line and reset buffer
+    if(c=='\n' || c=='\r'){
+      // increment line counter
+      counter++;
+
+      // read entry
+      // ignore empty lines
+      if(pos>0){
+	ret=sscanf(line, "%d %d %le %le", &kx, &ky, &r, &i);
+
+	// errors
+	if(ret!=4){
+	  fprintf(stderr, "warning: line %d does not match the input format: '%s'\n", counter, line);
+	}
+	else{
+	  if(kx>K1 || kx<-K1 || ky>K2 || ky<-K2){
+	    fprintf(stderr, "warning: reading line %d: kx or ky out of bounds: %d,%d\n", counter, kx, ky);
+	  }
+	  else{
+	    // set u
+	    u[klookup(kx, ky, 2*K1+1, 2*K2+1)]=r+i*I;
+	  }
+	}
+      }
+
+      // reset buffer
+      pos=0;
+      line[pos]='\0';
+      commented=false;
+    }
+    // comment: stop reading
+    else if (c=='#'){
+      commented=true;
+    }
+    // add to buffer (unless we are in a comment)
+    else if (!(commented)){
+      // check that there is room in buffer
+      if(pos==len){
+	// too short: reallocate
+	line_realloc=calloc(sizeof(char), 2*len);
+	for(pos=0;pos<len;pos++){
+	  line_realloc[pos]=line[pos];
+	}
+	free(line);
+	line=line_realloc;
+	len=2*len;
+      }
+
+      // add c to line
+      line[pos]=c;
+      pos++;
+      line[pos]='\0';
+    }
+  }
+
+  free(line);
+
+  return 0;
+}
-- 
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