From fb604ec3a0ffa3b4bc878bab374fdb8f0b6c919f Mon Sep 17 00:00:00 2001
From: Holden Rohrer <hr@hrhr.dev>
Date: Mon, 30 Mar 2020 02:10:05 -0400
Subject: queue-like string buffer (undocumented)

---
 buf.c | 123 ++++++++++++++++++++++++++++++++++++++++--------------------------
 buf.h |  16 ++++-----
 2 files changed, 82 insertions(+), 57 deletions(-)

diff --git a/buf.c b/buf.c
index eb1655e..b76fa0b 100644
--- a/buf.c
+++ b/buf.c
@@ -1,82 +1,109 @@
 #include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
 #include "buf.h"
 
-int max(int a, int b){
-    if (a > b) return a;
-    return b;
-}
-int min(int a, int b){
-    if (a < b) return a;
-    return b;
-}
+#define min(a,b) (a<b) ? a : b
 
 struct buf_node{
     char* text;
-    size_t space;
     struct buf_node* next;
-    struct buf_node* prev;
 };
 
 struct buf{
     buf_node* head;
     buf_node* tail;
     size_t cap;
-};
-
-buf* newbuf(size_t cap){
-    buf* buffer = malloc(sizeof(buf));
-    buffer->cap = cap;
-    buffer->tail = buffer->head = newbufnode(cap);
-    return buffer;
-}
+    size_t ins;
+    size_t pop;
+}; // a "thick" linked list (buffered for mem efficiency)
 
 buf_node* newbufnode(size_t cap){
-    buf_node* bufnode = calloc(sizeof(buf_node));
+    buf_node* bufnode = malloc(sizeof(buf_node));
     bufnode->text = malloc(sizeof(char)*cap);
     return bufnode;
 }
 
-void bextendbuf(buf* buffer){
-    buffer->tail = buffer->tail->prev->next
-    = buffer->tail->prev = newbufnode();
-}
-
-void fextendbuf(buf* buffer){
-    buffer->head = buffer->head->next->prev
-    = buffer->head->next = newbufnode();
+buf* newbuf(size_t cap){
+    buf* buffer = malloc(sizeof(buf));
+    buffer->tail = buffer->head = newbufnode(cap);
+    buffer->cap = cap;
+    buffer->ins = buffer->pop = 0;
+    return buffer;
 }
 
-void addchrbuf(buf* buffer, char chr){ // front
-    buf_node* head = buffer->head
-    if (head->space < 0 || head->space == buffer->cap)
-        fextendbuf(buffer);
-    *(head->text + head->space) = chr;
-    head->space++;
-}
-void addstrbuf(buf* buffer, char* str){
-    
+size_t buflen(buf* buffer){
+    buf_node* cur = buffer->tail;
+    size_t size = buffer->ins-buffer->pop+buffer->cap;
+    while (cur != buffer->head) {
+        cur = cur->next; // skips one iter        ^^^
+        size += buffer->cap;
+    };
+    return size;
 }
-char remchrbuf(buf* buffer){
 
+void extendbuf(buf* buffer){
+    buffer->head->next = newbufnode(buffer->cap);
+    buffer->head = buffer->head->next;
+    // buffer->ins = 0 is taken care of in the function that uses this.
 }
-char* remchrbuf(buf* buffer, int ct){
 
+void shortenbuf(buf* buffer){
+    buf_node* tmp = buffer->tail;
+    buffer->tail = buffer->tail->next;
+    free(tmp);
+    buffer->pop = 0;
 }
 
-void prechrbuf(buf* buffer, char chr){ // back
-
+char popchrbuf(buf* buffer){
+    if (buffer->pop == buffer->cap) shortenbuf(buffer);
+    buffer->pop++;
+    return buffer->tail->text[buffer->pop-1];
 }
-void prestrbuf(buf* buffer, char* str){
-
+char* popstrbuf(buf* buffer, size_t ct){
+    char* str = malloc((ct+1)*sizeof(char)); str[ct] = 0;
+    size_t rem;
+    for (size_t loc = 0; ct>loc; loc += rem){
+        if (buffer->pop == buffer->cap) shortenbuf(buffer);
+        rem = min(buffer->cap, ct-loc);
+        memcpy(str+loc, buffer->tail->text+buffer->pop, rem);
+        buffer->pop += rem;
+    } /* probably some inefficiencies here*/
+    return str;
 }
-char shfchrbuf(buf* buffer){
 
+void inschrbuf(buf* buffer, char chr){
+    if (buffer->ins == buffer->cap) extendbuf(buffer);
+    buffer->cap++;
+    buffer->head->text[buffer->cap-1] = chr;
 }
-char* shfstrbuf(buf* buffer, int ct){
-
+void insstrbuf(buf* buffer, char* str){
+    size_t len = strlen(str);
+    size_t tgt = min(len, buffer->cap - buffer->ins);
+    memcpy(buffer->head->text+buffer->ins, str, tgt);
+    buffer->ins += len;
+    buffer->ins %= buffer->cap;
+    for (;tgt<len; tgt += buffer->cap){
+        extendbuf(buffer);
+        memcpy(buffer->head->text, str+tgt, min(len-tgt, buffer->cap));
+    }
 }
 
-char* strpeekbuf(buf* buffer, int loc, int len){
-
+char* strpeekbuf(buf* buffer, size_t loc, size_t len){
+    char* str = malloc(sizeof(char)*(len+1)); str[len] = 0;
+    buf_node* start;
+
+    loc += buffer->ins;
+    for (start = buffer->tail; loc>0;
+            loc -= buffer->cap)
+        start = start->next; // start,loc is where one starts streaming
+    if (len > buffer->cap){
+        memcpy(str, start->text+loc, buffer->cap-loc);
+        len -= buffer->cap - loc;
+    }
+    for (; len > buffer->cap; len -= buffer->cap ){
+        memcpy(str, start->text, buffer->cap);
+    }
+    memcpy(str, start->text, len);
+    return str;
 }
-
diff --git a/buf.h b/buf.h
index 7323b83..808cd3f 100644
--- a/buf.h
+++ b/buf.h
@@ -6,16 +6,14 @@ typedef struct buf buf;
 
 buf* newbuf(size_t cap);
 
-void addchrbuf(buf* buffer, char chr); // front
-void addstrbuf(buf* buffer, char* str);
-char remchrbuf(buf* buffer);
-char* remstrbuf(buf* buffer, int ct);
+size_t buflen(buf* buffer);
 
-void prechrbuf(buf* buffer, char chr); // back
-void prestrbuf(buf* buffer, char* str);
-char shfchrbuf(buf* buffer);
-char* shfstrbuf(buf* buffer, int ct);
+char popchrbuf(buf* buffer);
+char* popstrbuf(buf* buffer, size_t ct);
 
-char* strpeekbuf(buf* buffer, int loc);
+void inschrbuf(buf* buffer, char chr);
+void insstrbuf(buf* buffer, char* str);
+
+char* strpeekbuf(buf* buffer, size_t loc, size_t len);
 
 #endif
-- 
cgit